View source for Sexual intercourse

{{short description|Penetrative sexual activity for reproduction or sexual pleasure}}
{{hatnote|This article is primarily about humans. For other animals, see [[Animal sexual behaviour]]. For other uses, see [[Sex (disambiguation)]].}}
{{redirect|Copulation|copulation among other animals|Copulation (zoology)|the biological functions of sexual intercourse|Penile-vaginal intercourse}}
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[[File:Paul Avril - Les Sonnetts Luxurieux (1892) de Pietro Aretino, 2.jpg|thumb|upright=1.35|Sexual intercourse in the [[missionary position]] depicted by [[Édouard-Henri Avril]] (1892)]]
'''Sexual intercourse''' (also '''coitus''' or '''copulation'''<!-- NOTE: "Sex" is not bolded as an alternative term. This is per WP:Alternative name and MOS:BOLD. It does not redirect here, and is mentioned lower in the lead. It is also a significantly broader term.
 -->) is a [[sexual activity]]<!-- NOTE: To align with WP:Due weight, the most common definition has been put forth first. "Coitus" and "copulation," which are the most common technical terms for sexual intercourse, are also being defined in the first sentence (for both humans and non-humans) and these terms, especially coitus, usually only mean penile–vaginal intercourse, as reported in various reliable sources (including those used to discuss the topic in the Definitions section below). The variant "sexual intercourse" is slightly more inclusive, but is additionally addressed in most sources and in the Definitions and Prevalence sections as most commonly meaning penile–vaginal intercourse.--> typically involving the insertion and [[Pelvic thrust|thrusting]] of the male [[Human penis|penis]] inside the female [[vagina]] for [[sexual pleasure]],  [[sexual reproduction|reproduction]], or both.<ref name="Most common">Sexual intercourse most commonly means penile–vaginal penetration for sexual pleasure or sexual reproduction; dictionary sources state that it especially means this, and scholarly sources over the years agree. See, for example;
* {{cite dictionary |title=Sexual intercourse |dictionary=[[Dictionary.com]] |url=https://www.dictionary.com/browse/sexual-intercourse |access-date=August 24, 2024}}
* {{cite dictionary |title=Sexual intercourse |dictionary=[[Merriam-Webster]] |url=http://www.merriam-webster.com/dictionary/sexual%20intercourse |access-date=August 24, 2024}}
* {{cite book |author=Richard M. Lerner |url=https://books.google.com/books?id=_wXasY1HyAYC&pg=PA193 |title=Handbook of Adolescent Psychology |author2=Laurence Steinberg |publisher=[[John Wiley & Sons]] |year=2004 |isbn=978-0-471-69044-3 |pages=193–196 |quote=When researchers use the term ''sex'', they nearly always mean sexual intercourse&nbsp;– more specifically, penile–vaginal intercourse. [...] The widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.' |author-link=Richard M. Lerner |author2-link=Laurence Steinberg |access-date=April 29, 2013}}
* {{cite book |author=Fedwa Malti-Douglas |author-link=Fedwa Malti-Douglas |url=https://archive.org/details/encyclopediaofse0000unse_i6t7 |title=Encyclopedia of Sex and Gender: A-C |publisher=[[Macmillan Publishers|Macmillan Reference]] |year=2007 |isbn=978-0-02-865961-9 |page=308 |quote=Sexual intercourse. [T]he term coitus indicates a specific act of sexual intercourse that also is known as coition or copulation. This 'coming together' is generally understood in heteronormative terms as the penetration of a woman's vagina by a man's penis. |url-access=registration}}
* {{cite book |author=Irving B. Weiner |url=https://books.google.com/books?id=pUSG1BONmekC&pg=PA1577 |title=The Corsini Encyclopedia of Psychology |author2=W. Edward Craighead |publisher=[[John Wiley & Sons]] |year=2010 |isbn=978-0-470-17023-6 |volume=4 |page=1577 |quote=Human sexual intercourse, or coitus, is one of the most common sexual outlets among adults. Sexual intercourse generally refers to penile penetration of the vagina. |author-link=Irving B. Weiner |access-date=August 21, 2013}}
* {{cite book |author=Clint E. Bruess |url=https://books.google.com/books?id=WWFW6-kkAVoC&pg=PA152 |title=Sexuality Education Theory and Practice |author2=Elizabeth Schroeder |publisher=[[Jones & Bartlett Publishers]] |year=2013 |isbn=978-1-4496-4928-9 |page=152 |quote=In many cultures around the world, vaginal sex is what is usually implied when people refer to 'having sex' or 'sexual intercourse.' It is the most frequently studied behavior and is often the focus of sexuality education programming for youth. |access-date=December 5, 2014}}
* {{cite book |author=Cecie Starr |url=https://books.google.com/books?id=lS5-BAAAQBAJ&pg=PT339 |title=Human Biology |author2=Beverly McMillan |publisher=[[Cengage Learning]] |year=2015 |isbn=978-1-305-44594-9 |page=339 |quote=Coitus and copulation are both technical terms for sexual intercourse. The male sex act involves an erection, in which the limp penis stiffens and lengthens. It also involves ejaculation, the forceful expulsion of semen into the urethra and out from the penis. [...] During coitus, pelvic thrusts stimulate the penis as well as the female's clitoris and vaginal wall. The stimulation triggers rhythmic, involuntary contractions in smooth muscle in the male reproductive tract, especially the vas deferens and the prostate. The contractions rapidly force sperm out of each epididymis. They also force the contents of seminal vesicles and the prostate gland into the urethra. The resulting mixture, semen, is ejaculated into the vagina. |access-date=December 27, 2017}}
* {{cite book |author=Janell L. Carroll |url=https://books.google.com/books?id=9A9EDwAAQBAJ&pg=PT289 |title=Sexuality Now: Embracing Diversity |publisher=[[Cengage Learning]] |year=2018 |isbn=978-1-337-67206-1 |page=289 |quote=Vaginal intercourse (also referred to as sexual intercourse) involves inserting the penis into the vagina. |access-date=November 22, 2019}}</ref> This is also known as '''vaginal intercourse''' or '''vaginal sex'''.<ref name="Alters">{{cite book| vauthors =Alters S| title = Essential Concepts for Healthy Living | publisher = [[Jones & Bartlett Publishers]] | year = 2012 | pages = 180–181|isbn = 978-1-4496-3062-1 | url=https://books.google.com/books?id=VegUiVbruBMC&pg=PA180|quote=Most heterosexuals are familiar with the notion of 'having sex' or sexual intercourse as vaginal sex, the insertion of a penis into a vagina. Vaginal sex, or coitus, is the most common and popular form of intimate sexual activity between partners.}}</ref><ref name="Carroll, 2018">{{cite book| vauthors = Carroll JL|title = Sexuality Now: Embracing Diversity| publisher = [[Cengage Learning]]| year = 2018 | page = 289|isbn = 978-1-337-67206-1| url =https://books.google.com/books?id=9A9EDwAAQBAJ&pg=PT289|quote=Vaginal intercourse (also referred to as sexual intercourse) involves inserting the penis into the vagina.}}</ref> Sexual penetration has been known by humans since the dawn of time, and has been an [[instinctive]] form of [[sexual behaviour]] and [[psychology]] among humans. Other forms of [[sexual penetration|penetrative]] sexual intercourse include [[anal sex]] (penetration of the [[Human anus|anus]] by the penis), [[oral sex]] (penetration of the mouth by the penis or oral penetration of the female [[genitalia]]), [[Fingering (sexual act)|fingering]] (sexual penetration by the fingers) and penetration by use of a [[dildo]] (especially a [[strap-on dildo]]), and [[Vibrator (sex toy)|vibrators]].<ref name="health.discovery.com">{{cite web |title=Sexual Intercourse |url=http://health.discovery.com/centers/sex/sexpedia/intercourse.html |archive-url=https://web.archive.org/web/20080822040701/http://health.discovery.com/centers/sex/sexpedia/intercourse.html |archive-date=August 22, 2008 |access-date=January 12, 2008 |publisher=[[Discovery Channel|Discovery Health]]}}</ref><ref name="Rathus">{{Cite book |url=https://archive.org/details/humansexualityin00rath_1 |title=Human Sexuality in a World of Diversity |vauthors=Rathus SA, Nevid JS, Rathus LF |publisher=[[Allyn & Bacon]] |year=2010 |isbn=978-0-205-78606-0 |page=251 |url-access=registration}}</ref> These activities involve [[physical intimacy]] between two or more people and are usually used among humans solely for physical or [[Emotional intimacy|emotional]] pleasure. They can contribute to [[human bonding]].<ref name=health.discovery.com/><ref name="Freberg">{{Cite book |url=https://archive.org/details/discoveringbiolo0002edfreb |title=Discovering Biological Psychology |vauthors=Freberg L |publisher=[[Cengage Learning]] |year=2009 |isbn=978-0-547-17779-3 |pages=308–310 |url-access=registration}}</ref>

There are different views on what constitutes sexual intercourse or other sexual activity, which can impact on views of [[sexual health]].<ref name="WHO, Sex">{{cite web |date=January 2002 |title=Defining sexual health: Report of a technical consultation on sexual health |url=https://www.who.int/reproductivehealth/topics/gender_rights/defining_sexual_health.pdf |archive-url=https://web.archive.org/web/20120906205203/https://www.who.int/reproductivehealth/topics/gender_rights/defining_sexual_health.pdf |archive-date=September 6, 2012 |access-date=September 5, 2012 |publisher=[[World Health Organization]] |page=4 |quote=In English, the term 'sex' is often used to mean 'sexual activity' and can cover a range of behaviours. Other languages and cultures use different terms, with slightly different meanings.}}</ref> Although ''sexual intercourse'', particularly the term ''coitus,'' generally denotes penile–vaginal penetration and the possibility of creating [[offspring]],<ref name="Most common"/> it also commonly denotes penetrative oral sex and penile–anal sex, especially the latter.<ref name="Oral and anal">* {{cite web |title=Sexual Intercourse |url=http://health.discovery.com/centers/sex/sexpedia/intercourse.html |archive-url=https://web.archive.org/web/20080822040701/http://health.discovery.com/centers/sex/sexpedia/intercourse.html |archive-date=August 22, 2008 |access-date=January 12, 2008 |publisher=[[Discovery Channel|Discovery.com]]}}
* {{cite book |author=Nancy W. Denney |url=https://archive.org/details/humansexuality0000denn_r0k2 |title=Human Sexuality |author2=David Quadagno |publisher=[[Mosby-Year Book]] |year=2008 |isbn=978-0-8016-6374-1 |page=273 |quote=Although the term intercourse is usually used to refer to the insertion of the penis into the vagina, it is also used to refer to oral intercourse or anal intercourse in which the penis is inserted into the mouth or the anus, respectively. |url-access=registration}}</ref> It usually encompasses sexual penetration, while [[non-penetrative sex]] has been labeled ''outercourse'',<ref name="Non-penetrative">
* {{Cite book| author = Ann O'Leary |author-link=Ann O'Leary (psychologist) | title =Beyond Condoms: Alternative Approaches to HIV Prevention| isbn = 978-0-306-46731-8| publisher = [[Springer Publishing|Springer]] | year = 2002|page =155|url=https://books.google.com/books?id=J3NT39hW474C&pg=PA155}}
* {{cite book|author=Dianne Hales|title=An Invitation to Health: Live It Now! Brief Edition|edition=3rd|isbn = 978-1-305-44595-6|publisher=[[Cengage Learning]]|year=2015|page=251|url=https://books.google.com/books?id=UTJBBAAAQBAJ&pg=PT251}}</ref> but non-penetrative sex may also be considered sexual intercourse.<ref name=health.discovery.com/><ref name="Kahn, Fawcett">{{cite book |url=https://archive.org/details/encyclopediaofme0000kahn |title=The Encyclopedia of Mental Health |vauthors=Kahn AP, Fawcett J |publisher=[[Infobase Publishing]] |year=2008 |isbn=978-0-8160-6454-0 |page=111 |url-access=registration}}</ref> ''Sex'', often a shorthand for ''sexual intercourse'', can mean any form of sexual activity.<ref name="WHO, Sex"/> Because people can be at risk of contracting [[sexually transmitted infections]] during these activities, [[safer sex]] practices are recommended by health professionals to reduce transmission risk.<ref name="Hales">{{Cite book |url=https://archive.org/details/invitationtoheal00hale_3 |title=An Invitation to Health Brief 2010–2011 |vauthors=Hales D |publisher=[[Cengage Learning]] |year=2008 |isbn=978-0-495-39192-0 |pages=269–271 |url-access=registration}}</ref><ref name="Kumar">{{Cite book|vauthors=Kumar B, Gupta S|title=Sexually Transmitted Infections| publisher = [[Elsevier Health Sciences]]|year = 2014|page=93|isbn = 978-81-312-2978-1|url=https://books.google.com/books?id=kQ9tAwAAQBAJ&pg=PA93}}</ref>

Various jurisdictions place restrictions on certain sexual acts, such as [[adultery]], [[incest]], sexual activity with [[minor (law)|minors]], [[prostitution]], [[rape]], [[zoophilia]], [[sodomy]], [[premarital sex]] and [[extramarital sex]]. [[Religious]] beliefs also play a role in personal decisions about sexual intercourse or other sexual activity, such as decisions about [[virginity]],<ref name="Carpenter"/><ref name="Intimate">{{Cite book |url=https://archive.org/details/marriagefamilyex00 |title=The Marriage and Family Experience: Intimate Relationship in a Changing Society |vauthors=Strong B, DeVault C, Cohen TF |publisher=[[Cengage Learning]] |year=2010 |isbn=978-0-534-62425-5 |page=186 |quote=Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. But occasionally we hear people speak of 'technical virginity' [...] Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins' [...] Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual sexual activity (e.g., oral sex, anal sex, or mutual masturbation). |access-date=October 8, 2011 |url-access=registration}}</ref> or legal and public policy matters. [[Religion and sexuality|Religious views on sexuality]] vary significantly between different religions and sects of the same religion, though there are common themes, such as prohibition of adultery.

Reproductive sexual intercourse between non-human animals is more often called ''[[Copulation (zoology)|copulation]]'', and [[sperm]] may be introduced into the female's reproductive tract in non-vaginal ways among the animals, such as by [[cloaca]]l copulation. For most non-human [[mammal]]s, [[mating]] and copulation occur at the point of [[Estrous cycle|estrus]] (the most fertile period of time in the female's reproductive cycle), which increases the chances of [[Internal fertilization|successful impregnation]].<ref name="Kent">{{Cite book| author =Michael Kent| title = Advanced biology| isbn = 978-0-19-914195-1| publisher = [[Oxford University Press]] | year = 2000 |pages =250–253|url=https://books.google.com/books?id=8aw4ZWLABQkC&pg=PA250|access-date=October 21, 2015}}</ref><ref name="Thorpe">{{Cite book| author = Showick Thorpe| author2 = Edgar Thorpe | title = The Pearson General Studies Manual 2009, 1/e | publisher = [[Pearson Education India]]| year = 2009 |page = 1.79 | isbn =978-81-317-2133-9 |url=https://books.google.com/books?id=oAo1X2eagywC&pg=RA1-PR17|access-date=October 21, 2015}}</ref> However, [[bonobo]]s, [[dolphin]]s and [[chimpanzees]] are known to engage in sexual intercourse regardless of whether the female is in estrus, and to engage in [[Homosexual behavior in animals|sex acts with same-sex partners]].<ref name="Non-human">
* {{Cite book|author1=Herbert L. Petri |author2=John M. Govern| title = Motivation: Theory, Research, and Application| year = 2012 | publisher = [[Cengage Learning]] |page= 24 | isbn = 978-1-285-40151-5 |url=https://books.google.com/books?id=DbwKAAAAQBAJ&pg=PA24}}
* {{cite journal |vauthors=Bailey NW, Zuk M | title = Same-sex sexual behavior and evolution | journal = Trends Ecol. Evol. | volume = 24 | issue = 8 | pages = 439–46 | date = August 2009 | pmid = 19539396 | doi = 10.1016/j.tree.2009.03.014 | bibcode = 2009TEcoE..24..439B  | issn=0169-5347}}</ref> Like humans engaging in sexual activity primarily for pleasure, this behavior in these animals is also presumed to be for pleasure, and a contributing factor to strengthening their social bonds.<ref name="Balcombe">{{Cite book|last=Balcombe|first=Jonathan|author-link= Jonathan Balcombe | title = Pleasurable Kingdom: Animals and the Nature of Feeling Good| year = 2006 |publisher = [[Palgrave Macmillan]] |pages= [https://archive.org/details/pleasurablekingd00balc_0/page/106 106]–118 | isbn = 978-0-230-55227-2|url=https://archive.org/details/pleasurablekingd00balc_0|url-access=registration}}</ref>
{{TOC limit|3}}

==Behaviors==
{{See also|Human sexual activity|Human sexuality}}

===Definitions===
[[File:Couple having sex.jpg|thumb|Modern artwork of a couple engaged in [[vaginal intercourse]]]]
[[File:Édouard-Henri Avril (18).jpg|thumb|19th-century [[Eroticism|erotic]] interpretation of Roman emperor [[Hadrian]] and [[Antinous]] engaged in anal intercourse, by [[Édouard-Henri Avril]]]]
<!-- NOTE: This section was titled "Etymology and definitions." As the etymology material is defining sexual intercourse, and there is little material on the etymology, there appears to be no need to have separate sections. Per MOS:PARAGRAPHS, "Short paragraphs and single sentences generally do not warrant their own subheading." The heading was subsequently shortened to "Definitions" and added as a subsection of the Behaviors section (since it includes researchers' views and general views on definitions and behaviors).-->

''Sexual intercourse'' may be called ''coitus'', ''copulation'', ''coition'', or ''intercourse''. ''Coitus'' is derived from the [[Latin]] word ''coitio'' or ''coire'', meaning "a coming together or joining together" or "to go together", and is known under different ancient Latin names for a variety of sexual activities, but usually denotes penile–vaginal penetration.<ref name="Coitus">
* {{cite dictionary|title=Coitus| date=August 14, 2024| dictionary=[[Merriam-Webster]]|url=http://www.merriam-webster.com/dictionary/coitus}}
* {{cite book| author = Fedwa Malti-Douglas |author-link=Fedwa Malti-Douglas |title = Encyclopedia of Sex and Gender: A-C |publisher = [[Macmillan Publishers|Macmillan Reference]] | year = 2007 | page = 308 |isbn = 978-0-02-865961-9 |quote=Sexual intercourse. [T]he term coitus indicates a specific act of sexual intercourse that also is known as coition or copulation. This 'coming together' is generally understood in heteronormative terms as the penetration of a woman's vagina by a man's penis.}}
* {{cite book|title = The Encyclopedia of Mental Health | publisher = [[Infobase Publishing]] | year = 2008 | page = 111|isbn = 978-0-8160-6454-0| url = https://books.google.com/books?id=tTFYIh-HcYYC&pg=PA111|author1=Ada P. Kahn |author2=Jan Fawcett }}
</ref> This is often called [[vaginal intercourse]] or ''vaginal sex.''<ref name="Alters"/><ref name="Carroll">See [https://books.google.com/books?id=gU3SZSh-eXsC&pg=PT334 page 302] for orgasm information, and [https://books.google.com/books?id=gU3SZSh-eXsC&pg=PT316 pages 285–286] for definitions, prevalence and length of sexual intercourse. {{cite book |vauthors=Carroll JL| title = Discovery Series: Human Sexuality| edition = 1st | publisher = [[Cengage Learning]]|pages=656 pages| isbn = 978-1-111-84189-8|year=2012|url=https://books.google.com/books?id=gU3SZSh-eXsC}}</ref> ''Vaginal sex,'' and less often ''vaginal intercourse'', may also denote any vaginal sexual activity, particularly if [[Sexual penetration|penetrative]], including [[lesbian sexual practices|sexual activity between lesbian couples]].<ref name="Harvey">{{cite book|vauthors = Milkman HB, Wanberg KW | title = Pathways to Self-Discovery and Change: Criminal Conduct and Substance Abuse Treatment for Adolescents | publisher = [[SAGE Publications|SAGE]] | year = 2004 | pages = 254–255|isbn = 978-1-4129-0614-2| url =https://books.google.com/books?id=2ovqg5jfsN0C&pg=PA254}}</ref><ref name="Kinetics">{{cite book| vauthors = Kinetics H | title = Health and Wellness for Life| publisher = Human Kinetics | year = 2009 | page = 207|isbn = 978-0-7360-6850-5| url =https://books.google.com/books?id=2GZ7N4wOeGYC&pg=PA207}}</ref> ''Copulation'', by contrast, more often denotes the [[mating]] process, especially for non-human animals; it can mean a variety of sexual activities between opposite-sex or [[same-sex pairings]],<ref name="Barrows">{{cite book| vauthors = Barrows EM| title = Animal Behavior Desk Reference: A Dictionary of Animal Behavior, Ecology, and Evolution | publisher = [[Taylor & Francis]] | year = 2011 | pages = 122–124 |isbn = 978-1-4398-3651-4 | url=https://books.google.com/books?id=2vf7ZbLENzEC&pg=PA122}}</ref> but generally means the [[Sexual reproduction|sexually reproductive]] act of transferring [[Spermatozoon|sperm]] from a male to a female or sexual procreation between a man and a woman.<ref name="Barrows"/><ref name="Copulation1">{{cite web|title=Copulation|publisher=[[Dorland's medical reference works|Dorland's Medical Dictionary for Health Consumers]], 2007/[[TheFreeDictionary.com]] for various dictionary definitions|access-date=September 6, 2012|url=http://medical-dictionary.thefreedictionary.com/copulation}}</ref><ref name="Copulation2">{{cite web|title=Copulation|publisher=[[The American Heritage Dictionary of the English Language]], Fifth Edition|year=2011|access-date=August 23, 2013|url=http://ahdictionary.com/word/search.html?q=Copulation}}</ref>

Although ''sex'' and ''having sex'' also most commonly denote penile–vaginal intercourse,<ref name="Most common2">
* {{cite book| author = Ken Plummer | author-link = Ken Plummer (sociologist) | title = Modern Homosexualities: Fragments of Lesbian and Gay Experiences | publisher = [[Routledge]] | year = 2002 | pages = 187–191 | access-date = August 24, 2013|isbn =978-1-134-92242-0 | url=https://books.google.com/books?id=OSO3q4XEfz4C&pg=PA189|quote=[S]ome sexual practices are regarded as inherently better (normal, natural, more satisfying) than others, with vaginal intercourse privileged as the 'Real Thing.' Such beliefs, influenced by views about sex as ultimately a reproductive function, continue to be perpetuated through discourses on sex despite a number of important contradictions.}}
* {{cite book | title = Handbook of Adolescent Psychology | publisher = [[John Wiley & Sons]] | year = 2004 | pages = 193–196 |isbn = 978-0-471-69044-3| url = https://books.google.com/books?id=_wXasY1HyAYC&pg=PA193|quote=When researchers use the term ''sex'', they nearly always mean sexual intercourse&nbsp;– more specifically, penile–vaginal intercourse... The widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.'| author = Richard M. Lerner| author-link = Richard M. Lerner| author2 = Laurence Steinberg| author2-link = Laurence Steinberg}}
* See [https://books.google.com/books?id=6qNCeI2AcY4C&pg=PT11 page 11 onwards] and [https://books.google.com/books?id=pXXZn_qSoDoC&pg=PA48 pages 47–49] for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. {{Cite book|author=Laura M. Carpenter|title=Virginity Lost: An Intimate Portrait of First Sexual Experiences|publisher=[[New York University|NYU Press]]|year = 2005|pages=295 pages |isbn=978-0-8147-1652-6|url=https://books.google.com/books?id=pXXZn_qSoDoC}}
* {{cite book| author = Fedwa Malti-Douglas|title = Encyclopedia of Sex and Gender: A-C| publisher = [[Macmillan Publishers|Macmillan Reference]] | year = 2007 | page = 308 |isbn = 978-0-02-865961-9|quote=Sexual intercourse. [T]he term coitus indicates a specific act of sexual intercourse that also is known as coition or copulation. This 'coming together' is generally understood in heteronormative terms as the penetration of a woman's vagina by a man's penis.}}
* {{cite book |author=Irving B. Weiner |author1-link=Irving B. Weiner |author2=W. Edward Craighead |title=The Corsini Encyclopedia of Psychology |volume=4 |publisher=[[John Wiley & Sons]] |year=2010 |page=1577 |access-date=August 21, 2013 |isbn=978-0-470-17023-6 |url=https://books.google.com/books?id=pUSG1BONmekC&pg=PA1577 |quote=Human sexual intercourse, or coitus, is one of the most common sexual outlets among adults. Sexual intercourse generally refers to penile penetration of the vagina.}}
* {{cite book| author = Clint E. Bruess| author2 = Elizabeth Schroeder|title = Sexuality Education Theory and Practice| publisher = [[Jones & Bartlett Publishers]] | year = 2013 | page = 152 |isbn = 978-1-4496-4928-9| url =https://books.google.com/books?id=WWFW6-kkAVoC&pg=PA152|quote=In many cultures around the world, vaginal sex is what is usually implied when people refer to 'having sex' or 'sexual intercourse'. It is the most frequently studied behavior and is often the focus of sexuality education programming for youth.}}</ref> ''sex'' can be significantly broad in its meaning and may cover any penetrative or [[non-penetrative sex|non-penetrative]] sexual activity between two or more people.<ref name="WHO, Sex"/> The [[World Health Organization]] (WHO) states that non-English languages and cultures use different words for sexual activity, "with slightly different meanings".<ref name="WHO, Sex"/> Various [[vulgarisms]], [[slang]], and [[euphemism]]s are used for sexual intercourse or other sexual activity, such as ''[[fuck]]'', ''screw'', ''shag'', and the phrase "sleep together".<ref name="Fuck">{{cite dictionary|title=Fuck|dictionary=[[Merriam-Webster]]|access-date=March 30, 2013|url=http://www.merriam-webster.com/dictionary/fuck}}</ref><ref>{{cite dictionary|title=Shag|dictionary=[[Merriam-Webster]]|access-date=March 30, 2013|url=http://www.merriam-webster.com/dictionary/shag}}</ref><ref name="Sleep together">{{cite web|title=Sleep together|publisher=[[TheFreeDictionary.com]]|access-date=March 30, 2013|url=http://www.thefreedictionary.com/sleep+together}}</ref> The laws of some countries use the euphemism, [[carnal knowledge]]. Penetration of the vagina by the [[Erection|erect]] penis is additionally known as ''intromission'', or by the Latin name ''[[wikt:immissio#Latin|immissio]] [[wikt:penis#Latin|penis]]'' (Latin for "insertion of the penis").<ref name="Intromission">{{cite dictionary|title=Intromission| dictionary=[[Merriam-Webster]]|access-date=December 26, 2012|url=http://www.merriam-webster.com/dictionary/intromission}}</ref> The age of first sexual intercourse is called ''sexarche''.<ref>{{cite web |title=sexarche - oi |publisher=Oxford University Press |work=Concise Medical Dictionary |url=http://oxfordindex.oup.com/view/10.1093/oi/authority.20110803100457655 |access-date=July 4, 2017 |archive-date=June 24, 2019 |archive-url=https://web.archive.org/web/20190624230226/https://oxfordindex.oup.com/view/10.1093/oi/authority.20110803100457655 |url-status=dead}}</ref><ref name="LaraAbdo2016">{{cite journal|vauthors=Lara LS, Abdo CH|title=Age at Time of Initial Sexual Intercourse and Health of Adolescent Girls|journal=Journal of Pediatric and Adolescent Gynecology|volume=29|issue=5|year=2016|pages=417–423|issn=1083-3188|doi=10.1016/j.jpag.2015.11.012|pmid=26655691}}</ref>

Vaginal, anal and oral sex are recognized as sexual intercourse more often than other sexual behaviors.<ref name="Most common forms">
* {{cite web| title= Sexual Intercourse | publisher=[[Discovery Channel|Discovery.com]]| access-date=January 12, 2008 | url=http://health.discovery.com/centers/sex/sexpedia/intercourse.html |archive-url =https://web.archive.org/web/20080822040701/http://health.discovery.com/centers/sex/sexpedia/intercourse.html|archive-date = August 22, 2008}}
* {{cite book|author = Harvey B. Milkman|author2 = Kenneth W. Wanberg | title = Pathways to Self-Discovery and Change: Criminal Conduct and Substance Abuse Treatment for Adolescents | publisher = [[SAGE Publications|SAGE]] | year = 2004 | pages = 254–255|isbn = 978-1-4129-0614-2| url =https://books.google.com/books?id=2ovqg5jfsN0C&pg=PA254}}
* {{cite book| author = Nancy W. Denney| author2 = David Quadagno | title = Human Sexuality | publisher = [[Mosby-Year Book]] | year = 2008 | page = 273|isbn = 978-0-8016-6374-1}}</ref> Sexual activity that does not involve penile-vaginal sex or other sexual penetration might be used to retain virginity (sometimes called [[technical virginity]]) or labeled ''outercourse''.<ref name="Technical virginity">
* See [https://books.google.com/books?id=6qNCeI2AcY4C&pg=PT11 page 11 onwards] and [https://books.google.com/books?id=pXXZn_qSoDoC&pg=PA48 pages 47–49] for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. {{Cite book|author=Laura M. Carpenter|title=Virginity Lost: An Intimate Portrait of First Sexual Experiences|publisher=[[New York University|NYU Press]]|year = 2005|access-date=October 9, 2011|pages=295 pages |isbn=978-0-8147-1652-6|url=https://books.google.com/books?id=pXXZn_qSoDoC}}
* {{Cite book|author1=Bryan Strong |author2=Christine DeVault |author3=Theodore F. Cohen |author1-link=Bryan Strong |title=The Marriage and Family Experience: Intimate Relationship in a Changing Society| publisher = [[Cengage Learning]]|year = 2010|page = 186| isbn = 978-0-534-62425-5|url=https://books.google.com/books?id=qjvoSOMB5JMC&pg=PA186|quote=Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. ...But occasionally we hear people speak of 'technical virginity' ... Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual activity (e.g. oral sex, anal sex, or mutual masturbation). ... Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins'.}}
* {{cite book | title = Our Sexuality | publisher = [[Cengage Learning]] | year = 2010 | pages = 286–289 |isbn = 978-0-495-81294-4| url = https://books.google.com/books?id=MpRnPtmdRVwC&pg=PA286|quote=Noncoital forms of sexual intimacy, which have been called outercourse, can be a viable form of birth control. Outercourse includes all avenues of sexual intimacy other than penile–vaginal intercourse, including kissing, touching, mutual masturbation, and oral and anal sex. |author1=Robert Crooks |author2=Karla Baur }}
* {{cite book|vauthors=UD, TK|title =Promoting Healthy Behaviour: A Practical Guide | publisher = [[Routledge]] | year = 2014 | pages = 243–248|isbn =978-1-317-81887-8| url =https://books.google.com/books?id=63XMAgAAQBAJ&pg=PA243}}</ref> One reason virginity loss is often based on penile–vaginal intercourse is because heterosexual couples may engage in anal or oral sex as a way of being sexually active while maintaining that they are virgins since they have not engaged in the reproductive act of coitus.<ref name="Technical virginity 2">
* See [https://books.google.com/books?id=6qNCeI2AcY4C&pg=PT11 page 11 onwards] and [https://books.google.com/books?id=pXXZn_qSoDoC&pg=PA48 pages 47–49] for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. {{Cite book|author=Laura M. Carpenter|title=Virginity Lost: An Intimate Portrait of First Sexual Experiences|publisher=[[New York University|NYU Press]]|year = 2005|access-date=October 9, 2011|pages=295 pages |isbn=978-0-8147-1652-6|url=https://books.google.com/books?id=pXXZn_qSoDoC}}
* {{Cite book|author1=Bryan Strong |author2=Christine DeVault |author3=Theodore F. Cohen |author1-link=Bryan Strong |title=The Marriage and Family Experience: Intimate Relationship in a Changing Society| publisher = [[Cengage Learning]]|year = 2010|page = 186| isbn = 978-0-534-62425-5|url=https://books.google.com/books?id=qjvoSOMB5JMC&pg=PA186|quote=Most people agree that we maintain virginity as long as we refrain from sexual (vaginal) intercourse. ...But occasionally we hear people speak of 'technical virginity' ... Other research, especially research looking into virginity loss, reports that 35% of virgins, defined as people who have never engaged in vaginal intercourse, have nonetheless engaged in one or more other forms of heterosexual activity (e.g. oral sex, anal sex, or mutual masturbation). ... Data indicate that 'a very significant proportion of teens ha[ve] had experience with oral sex, even if they haven't had sexual intercourse, and may think of themselves as virgins'.}}
* {{cite book|vauthors=UD, TK|title =Promoting Healthy Behaviour: A Practical Guide | publisher = [[Routledge]] | year = 2014 | pages = 243–248|isbn =978-1-317-81887-8| url = https://books.google.com/books?id=63XMAgAAQBAJ&pg=PA243}}</ref> Some [[gay men]] consider [[frot]] or oral sex as a way of maintaining their virginities, with penile-anal penetration used as sexual intercourse and for virginity loss, while other gay men may consider frot or oral sex as their main forms of sexual activity.<ref name="Carpenter"/><ref name="Virgin">{{cite magazine|vauthors=Gross MJ|title = Like a Virgin|id = 0001-8996|magazine=[[The Advocate (LGBT magazine)|The Advocate]]|publisher=[[Here Media]]|year=2003|pages=44–45|access-date=March 13, 2011|url=https://books.google.com/books?id=eWQEAAAAMBAJ&pg=PA44}}</ref><ref name="Dolby">{{cite magazine|vauthors=Dolby T|title=Why Some Gay Men Don't Go All The Way|magazine=[[Out (magazine)|Out]]|date=February 2004|access-date=February 12, 2011|pages=76–77|publisher=Here|url=https://books.google.com/books?id=jmIEAAAAMBAJ&pg=PA76}}</ref> Lesbians may categorize oral sex or [[Fingering (sexual act)|fingering]] as sexual intercourse and subsequently an act of virginity loss,<ref name="Carpenter">See [https://books.google.com/books?id=6qNCeI2AcY4C&pg=PT11 page 11 onwards] and [https://books.google.com/books?id=pXXZn_qSoDoC&pg=PA48 pages 47–49] for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. {{Cite book|vauthors=Carpenter LM|title=Virginity Lost: An Intimate Portrait of First Sexual Experiences|publisher=[[New York University|NYU Press]]|year = 2005|pages=295 pages |isbn=978-0-8147-1652-6|url=https://books.google.com/books?id=pXXZn_qSoDoC}}</ref><ref name="Lerner">{{cite book|vauthors=Lerner RM, Steinberg L|title = Handbook of Adolescent Psychology | publisher = [[John Wiley & Sons]] | year = 2004 | pages = 193–196 |isbn = 978-0-471-69044-3| url = https://books.google.com/books?id=_wXasY1HyAYC&pg=PA193|quote=When researchers use the term ''sex'', they nearly always mean sexual intercourse&nbsp;– more specifically, penile–vaginal intercourse... The widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.'}}</ref> or [[tribadism]] as a primary form of sexual activity.<ref name="Greenberg">{{cite book|vauthors=Greenberg JS, Bruess CE, Conklin SC|title= Exploring the Dimensions of Human Sexuality|id = 9780763741488|publisher=[[Jones & Bartlett Learning]]|year=2007|page=429|url=https://books.google.com/books?id=ZdYh_iFZvbkC&pg=PA429|isbn =978-0-7637-4148-8}}</ref><ref name="Weiten3">{{cite book|vauthors=Weiten W, Dunn DS, Hammer EY|title=Psychology Applied to Modern Life: Adjustment in the 21st Century|id =1305968476|publisher=[[Cengage Learning]]|year=2016|page=349|isbn =978-0-7637-4148-8|access-date=December 27, 2017|url=https://books.google.com/books?id=09S5DQAAQBAJ&pg=PA349}}</ref>

Researchers commonly use ''sexual intercourse'' to denote penile–vaginal intercourse while using specific words, such as ''anal sex'' or ''oral sex'', for other sexual behaviors.<ref name="Researchers">
* {{cite book|title= Exploring Human Sexuality: Making Healthy Decisions|id = 9780763741488|publisher=[[Allyn & Bacon]]|year=2003|page=229|isbn =978-0-205-38059-6|author1=Richard D. McAnulty |author2=M. Michele Burnette }}
* {{cite book | title = Handbook of Adolescent Psychology | publisher = [[John Wiley & Sons]] | year = 2004 | pages = 193–196 |isbn = 978-0-471-69044-3| url = https://books.google.com/books?id=_wXasY1HyAYC&pg=PA193|quote=When researchers use the term ''sex'', they nearly always mean sexual intercourse&nbsp;– more specifically, penile–vaginal intercourse... The widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question matches what the researcher had in mind.'| author = Richard M. Lerner| author-link = Richard M. Lerner| author2 = Laurence Steinberg| author2-link = Laurence Steinberg}}
* See [https://books.google.com/books?id=6qNCeI2AcY4C&pg=PT11 page 11 onwards] and [https://books.google.com/books?id=pXXZn_qSoDoC&pg=PA48 pages 47–49] for views on what constitutes virginity loss and therefore sexual intercourse or other sexual activity; source discusses how gay and lesbian individuals define virginity loss, and how the majority of researchers and heterosexuals define virginity loss/"technical virginity" by whether a person has engaged in penile–vaginal sex. {{Cite book|author=Laura M. Carpenter|title=Virginity Lost: An Intimate Portrait of First Sexual Experiences|publisher=[[New York University|NYU Press]]|year = 2005|access-date=October 9, 2011|pages=295 pages |isbn=978-0-8147-1652-6|url=https://books.google.com/books?id=pXXZn_qSoDoC}}
* {{cite book | title = Handbook of Health Psychology | edition = 2nd|publisher = [[Psychology Press]] | year = 2012 | pages = 259–260 |isbn = 978-0-8058-6461-8| url =https://books.google.com/books?id=FZOjc8ouMlsC&pg=PA259|author1=Andrew Baum |author2=Tracey A. A. Revenson |author3=Jerome Singer }}
* {{cite book|vauthors=Aggleton P, Ball A, Mane P|title = Sex, Drugs and Young People: International Perspectives| publisher = [[Routledge]] | year = 2013 | page = 74|isbn =978-1-134-33310-3| url =https://books.google.com/books?id=HWcnAAAAQBAJ|quote=Having started with a discussion of penile-vaginal intercourse as the act that designates sexual initiation, as defined in most studies, we would like to undercut that position by stressing the need to define sex more broadly.}}</ref> Scholars [[Richard M. Lerner]] and [[Laurence Steinberg]] state that researchers also "rarely disclose" how they conceptualize sex "or even whether they resolved potential discrepancies" in conceptualizations of sex.<ref name="Lerner"/> Lerner and Steinberg attribute researchers' focus on penile–vaginal sex to "the larger culture's preoccupation with this form of sexual activity", and have expressed concern that the "widespread, unquestioned equation of penile–vaginal intercourse with sex reflects a failure to examine systematically 'whether the respondent's understanding of the question [about sexual activity] matches what the researcher had in mind'".<ref name="Lerner"/> This focus can also relegate other forms of mutual sexual activity to [[foreplay]] or contribute to them not being regarded as "real sex", and limits the meaning of [[rape]].<ref name="Baum">{{cite book |vauthors=McClelland SI |veditors=Baum A, Revenson TA, Singer J |chapter=Measuring Sexual Quality of Life: Ten Recommendations for Health Psychologists |title=Handbook of Health Psychology |edition=2nd |publisher=[[Psychology Press]] |year=2012 |pages=259–260 |access-date=April 30, 2013 |isbn=978-0-8058-6461-8 |chapter-url=https://books.google.com/books?id=FZOjc8ouMlsC&pg=PA259}}</ref><ref name="Kalbfleisch">{{cite book|vauthors= Kalbfleisch PJ, Cody MJ| title = Gender Power and Communication in Human Relationships | publisher = [[Routledge]] | year = 2012 | page = 153 | access-date = April 30, 2013|isbn = 978-1-136-48050-8| url = https://books.google.com/books?id=LyMo1RUJwj0C&pg=PA153}}</ref> It may also be that conceptually conflating sexual activity with vaginal intercourse and sexual function hinders and limits information about sexual behavior that [[non-heterosexual]] people may be engaging in, or information about heterosexuals who may be engaging in non–vaginal sexual activity.<ref name="Baum"/>

Studies regarding the meaning of sexual intercourse sometimes come into conflict. While most consider penile–vaginal intercourse to be sex, whether anal or oral intercourse are considered sex is more debatable, with oral sex ranking lowest.<ref name="Upton">{{cite book|vauthors=UD, TK|title =Promoting Healthy Behaviour: A Practical Guide | publisher = [[Routledge]] | year = 2014 | pages = 243–248|isbn =978-1-317-81887-8| url =https://books.google.com/books?id=63XMAgAAQBAJ&pg=PA243}}</ref><ref name="Aggleton 1">{{cite book|vauthors=Aggleton P, Ball A, Mane P|title = Sex, Drugs and Young People: International Perspectives| publisher = [[Routledge]] | year = 2013 | pages = 74–75|isbn =978-1-134-33310-3| url =https://books.google.com/books?id=HWcnAAAAQBAJ}}</ref> The [[Centers for Disease Control and Prevention]] (CDC) stated that "although there are only limited national data about how often adolescents engage in oral sex, some data suggest that many adolescents who engage in oral sex do not consider it to be 'sex'; therefore they may use oral sex as an option to experience sex while still, in their minds, remaining abstinent".<ref name="CDC, oral sex">{{cite web|title=Oral Sex and HIV Risk |date=June 2009 |access-date=August 30, 2013 |publisher=[[Centers for Disease Control and Prevention]] (CDC) |url=https://www.cdc.gov/hiv/resources/Factsheets/pdf/oralsex.pdf |url-status=dead |archive-url=https://web.archive.org/web/20130510210937/http://www.cdc.gov/hiv/resources/Factsheets/pdf/oralsex.pdf |archive-date=May 10, 2013 }}</ref> Upton et al. stated, "It is possible that individuals who engage in oral sex, but do not consider it as 'sex', may not associate the acts with the potential health risks they can bring."<ref name="Upton"/> In other cases, [[condom]] use is a factor, with some men stating that sexual activity involving the protection of a condom is not "real sex" or "the real thing".<ref name="Engel">{{cite book| author = Jonathan Engel | title = The Epidemic: A History of Aids | publisher = [[HarperCollins]] | year = 2009 | page = 242 | access-date = August 30, 2013 |isbn = 978-0-06-185676-1| url = https://books.google.com/books?id=GQud7Hf6oLIC&pg=PT242|quote=Many men simply did not like the feel of condoms, or associated them with emasculation. They say, 'Unless it's flesh on flesh, it's not real sex...}}</ref><ref name="Wekwete">{{cite book| author = Naomi N. Wekwete | title = Adolescent Pregnancy Challenges in the Era of HIV and AIDS: A Case Study of a Selected Rural Area in Zimbabwe | publisher = African Books Collective | year = 2010 | page = 49 | access-date = August 30, 2013 |isbn = 978-99944-55-48-5| url=https://books.google.com/books?id=LB45dcqSOpsC&pg=PA49}}</ref> This view is common among men in Africa,<ref name="Engel"/><ref name="Wekwete"/> where sexual activity involving the protection of a condom is often associated with [[emasculation]] because condoms prevent direct penile–to–skin genital contact.<ref name="Engel"/>

===Stimulation===
Sexual intercourse or other sexual activity can encompass various [[sexually stimulating]] factors ([[Stimulus (physiology)|physiological stimulation]] or [[Stimulus (psychology)|psychological stimulation]]), including different [[sex position]]s (such as the [[missionary position]], the most common human sex position<ref name=":0">[[Julian Monge Najera|Monge-Nájera, J.]], Rodríguez, M., & González, M. I. (2017). [https://revistas.uned.ac.cr/index.php/cuadernos/article/view/1679/1899 Time to deconstruct the concepts of "foreplay" and "intercourse": the real structure of human sexual encounters]. {{ill|Cuadernos de Investigación UNED|es}}, 9(1), 59-64.</ref>) or the use of [[sex toy]]s.<ref name="Weiten, 2008">{{cite book |title=Psychology Applied to Modern Life: Adjustment in the 21st Century |isbn = 978-0-495-55339-7 |publisher=[[Cengage Learning]] |year=2008 |pages=422–423 |access-date=January 5, 2012 |url=https://archive.org/details/isbn_2900495553396/page/422/ |author1=Wayne Weiten |author2=Margaret A. Lloyd |author3=Dana S. Dunn |author4=Elizabeth Yost Hammer |quote=The man-above, or "missionary," position is the most common [[sex position]].}}</ref><ref name="Taormino">{{cite book |last=Taormino |first=Tristan |author-link=Tristan Taormino |title=The Big Book of Sex Toys|publisher=Quiver|year=2009 |access-date=June 9, 2014|page=52|isbn=978-1-59233-355-4|url=https://books.google.com/books?id=Hfly-iMkWRkC&pg=PA52}}</ref> [[Foreplay]] may precede some sexual activities, often leading to [[sexual arousal]] of the partners and resulting in the erection of the [[Human penis|penis]] or [[Vaginal lubrication|natural lubrication]] of the [[vagina]].<ref name="Weiten, 2011">{{cite book|title=Psychology Applied to Modern Life: Adjustment in the 21st Century|isbn =978-1-111-18663-0|publisher=[[Cengage Learning]]|year=2011|pages=384–386|access-date=January 5, 2012|url=https://books.google.com/books?id=CGu96TeAZo0C&pg=PT421 |author1=Wayne Weiten |author2=Dana S. Dunn |author3=Elizabeth Yost Hammer }}</ref> It is also common for people to be as sexually satisfied by being kissed, touched [[eroticism|erotically]], or held as they are during sexual intercourse.<ref name="Alters2">{{cite book| author = Sandra Alters| author2 = Wendy Schiff|title =Essential Concepts for Healthy Living Update|publisher = [[Jones & Bartlett Publishers]] | year = 2011 | page = [https://archive.org/details/essentialconcept00sand_1/page/154 154] | access-date = December 9, 2014 |isbn = 978-1-4496-5374-3| url =https://archive.org/details/essentialconcept00sand_1| url-access = registration}}</ref>

Non-[[primate]] females copulate only when in [[estrus]],<ref name="Pfaus2015"/> but sexual intercourse is possible at any time of the [[menstrual cycle]] for women.<ref name="Reis"/><ref name="Dixson2012">Dixson A.F. (2012) [https://global.oup.com/academic/product/primate-sexuality-9780199676613?cc=fr&lang=en& ''Primate sexuality: Comparative studies of the Prosimians, Monkeys, Apes, and Human Beings.''] Oxford University Press, 2nd edition.</ref> [[Sex pheromones]] facilitate copulatory reflexes in various organisms, but, [[Human sex pheromones|in humans]], the detection of pheromones is impaired and they have only residual effects.<ref name="doty2014">Doty R.L. (2014) [https://www.ncbi.nlm.nih.gov/books/NBK200980/ {{lang|en|Human Pheromones: Do They Exist?}}] in Mucignat-Caretta C. (Ed). ''Neurobiology of Chemical Communication.'' Boca Raton (FL): CRC Press, (19).</ref> Non-primate females put themselves in the crucial [[lordosis position]] and remain motionless, but these motor copulatory reflexes are no longer functional in women.<ref name="Pfaus2015">Pfaus J.G., Flanagan-Cato L.M., Blaustein J.D. (2015) Female sexual behavior. in Plant T., Zeleznik A. (Eds). Knobil and Neill's Physiology of Reproduction. Academic Press, 4th edition</ref>

[[File:Édouard-Henri Avril (14).jpg|thumb|left|[[Édouard-Henri Avril]] depiction of a [[woman on top position]], a position that is more likely to stimulate the clitoris<ref name="Roberts">{{cite book|title=Sex|publisher=Lotus Press|year=2006|page=145|isbn = 978-81-89093-59-4|access-date=August 17, 2012|url=https://books.google.com/books?id=zDS9kC03x2IC&pg=PA145|author=Keath Roberts}}</ref>]]
During coitus, the partners orient their hips to allow the penis to move back and forth in the vagina to cause friction, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasm in either or both partners is achieved.<ref name="Kahn, Fawcett"/><ref name="Starr2">{{cite book|title=Human Biology|isbn =978-0-495-56181-1|publisher=[[Cengage Learning]]|year=2008|page=314|access-date=April 30, 2013|url=https://books.google.com/books?id=09reWGhFDqUC&pg=PA314|author1=Cecie Starr |author2=Beverly McMillan }}</ref>

For human females, stimulation of the [[clitoris]] plays a significant role in sexual activity; 70–80% of women require direct clitoral stimulation to achieve orgasm,<ref name="Flaherty">{{cite book|title=Psychiatry: Diagnosis & therapy. A Lange clinical manual|isbn=978-0-8385-1267-8|publisher=[[Appleton & Lange]] (Original from Northwestern University)|year=1993|pages=[https://archive.org/details/psychiatrydiagno00flah/page/544 544 pages]|url=https://archive.org/details/psychiatrydiagno00flah/page/544|quote=The amount of time of sexual arousal needed to reach orgasm is variable&nbsp;— and usually much longer&nbsp;— in women than in men; thus, only 20–30% of women attain a coital climax. b. Many women (70–80%) require manual clitoral stimulation...|author1=Joseph A. Flaherty|author2=John Marcell Davis|author3=Philip G. Janicak}}</ref><ref name="Kenneth Mah">{{cite journal |vauthors=Mah K, Binik YM | title = The nature of human orgasm: a critical review of major trends | journal = [[Clinical Psychology Review]] | volume = 21 | issue = 6 | pages = 823–856 |date=January 7, 2001 | pmid = 11497209 | doi = 10.1016/S0272-7358(00)00069-6 | quote = Women rated clitoral stimulation as at least somewhat more important than vaginal stimulation in achieving orgasm; only about 20% indicated that they did not require additional clitoral stimulation during intercourse.}}</ref><ref name="Kammerer-Doak">{{cite journal |vauthors=Kammerer-Doak D, Rogers RG | title = Female Sexual Function and Dysfunction | journal = Obstetrics and Gynecology Clinics of North America | volume = 35 | issue = 2 | pages = 169–183 |date=June 2008 | pmid = 18486835 | doi = 10.1016/j.ogc.2008.03.006 | quote = Most women report the inability to achieve orgasm with vaginal intercourse and require direct clitoral stimulation ... About 20% have coital climaxes...}}</ref> though indirect clitoral stimulation (for example, via vaginal intercourse) may also be sufficient (see [[Vaginal orgasm|orgasm in females]]).<ref name="Lloyd">{{cite book |first=Elisabeth Anne|last=Lloyd|title=The case of the female orgasm: bias in the science of evolution|isbn = 978-0-674-01706-1|publisher=Harvard University Press|year=2005|page=53|access-date=January 5, 2012 |url=https://books.google.com/books?id=6GFNvA6TvlwC&pg=PA53|oclc=432675780}}</ref><ref name="O'Connell">{{cite journal |vauthors=O'Connell HE, Sanjeevan KV, Hutson JM | s2cid = 26109805 | title = Anatomy of the clitoris | journal = The Journal of Urology | volume = 174 | issue = 4 Pt 1 | pages = 1189–95 | date = October 2005 | pmid = 16145367 | doi = 10.1097/01.ju.0000173639.38898.cd }}<br />{{cite web |last=Mascall |first=Sharon |title=Time for rethink on the clitoris | url = http://news.bbc.co.uk/2/hi/health/5013866.stm | date =June 11, 2006 | work = [[BBC News]] }}</ref> Because of this, some couples may engage in the [[woman on top position]] or the [[coital alignment technique]], a technique combining the "riding high" variation of the missionary position with pressure-counterpressure movements performed by each partner in rhythm with sexual penetration, to maximize clitoral stimulation.<ref name="Roberts"/><ref name="Hurlbert">{{cite journal |vauthors=Hurlbert DF, Apt C | title = The coital alignment technique and directed masturbation: a comparative study on female orgasm | journal = [[Journal of Sex & Marital Therapy]] | volume = 21 | issue = 1 | pages = 21–29 | year = 1995 | pmid = 7608994 | doi = 10.1080/00926239508405968 }}</ref>
[[File:Édouard-Henri Avril (24).jpg|thumb|right|[[Édouard-Henri Avril]] depiction of [[cunnilingus]] in the life of [[Sappho]]]]
Anal sex involves stimulation of the [[Human anus|anus]], anal cavity, sphincter valve or [[rectum]]; it most commonly means the insertion of a man's penis into another person's rectum, but may also mean the use of sex toys or fingers to penetrate the anus, or oral sex on the anus ([[anilingus]]), or [[Pegging (sexual practice)|pegging]].<ref name="Answer">{{cite book|author1-link=Barry Komisaruk|author1=Barry R. Komisaruk|author2=Beverly Whipple|author2-link=Beverly Whipple|author3=Sara Nasserzadeh|author3-link=Sara Nasserzadeh|author4 =Carlos Beyer-Flores|title=The Orgasm Answer Guide|isbn = 978-0-8018-9396-4|publisher=[[JHU Press]]|year=2009|pages=[https://archive.org/details/orgasmanswerguid00komi/page/108 108]–109|access-date=November 6, 2011|url=https://archive.org/details/orgasmanswerguid00komi|url-access =registration}}</ref>

Oral sex consists of all the sexual activities that involve the use of the mouth and throat to stimulate [[genitalia]] or anus. It is sometimes performed to the exclusion of all other forms of sexual activity, and may include the ingestion or absorption of semen (during [[fellatio]]) or vaginal fluids (during [[cunnilingus]]).<ref name="Weiten, 2008"/><ref name="Kamen">{{Cite book| author = Paula Kamen| title = Her Way: Young Women Remake the Sexual Revolution | isbn = 978-0-8147-4733-9| publisher = [[New York University Press]]| year = 2000|pages = 74–77| access-date=September 5, 2012|url=https://books.google.com/books?id=9bXq3Qc4py0C&pg=PA74}}</ref>

Fingering involves the digital manipulation of the clitoris, rest of the [[vulva]], vagina or anus for the purpose of sexual arousal and sexual stimulation; it may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities.<ref name="Kinetics"/><ref name="Hite">{{cite book|last=Hite|first=Shere|author-link=Shere Hite|title=The Hite Report: A Nationwide Study of Female Sexuality |publisher=[[Seven Stories Press]]|year=2003|location=New York, NY|pages=512 pages|isbn=978-1-58322-569-1|access-date=March 2, 2012|url=https://books.google.com/books?id=s3OZaVn2wfkC&pg=PP1}}</ref><ref name="Carroll2">{{cite book | title =Sexuality Now: Embracing Diversity | publisher = [[Cengage Learning]] | year = 2009 | pages = 118, 252, and 264 | access-date =June 23, 2012 | url = https://books.google.com/books?id=5f8mQx7ULs4C&pg=PA118|isbn =978-0-495-60274-3| first = Janell L. | last = Carroll}}
</ref>

===Reproduction===
{{Main|Sexual reproduction|Human reproduction}}
[[File:Pregnancy chance by day near ovulation.jpg|thumb|Chance of [[human fertilization|fertilization]] by [[menstrual cycle]] day relative to ovulation<ref name="DunsonBaird1999">{{cite journal|last1=Dunson|first1=D.B.|author1-link=David Dunson|last2=Baird|first2=D.D.|author2-link=Donna Baird|last3=Wilcox|first3=A.J.|last4=Weinberg|first4=C.R.|author4-link=Clarice Weinberg|title=Day-specific probabilities of clinical pregnancy based on two studies with imperfect measures of ovulation|journal=Human Reproduction|volume=14|issue=7|year=1999|pages=1835–1839|issn=1460-2350|doi=10.1093/humrep/14.7.1835|pmid=10402400|doi-access=free}}</ref>]]
[[File:Coition of a Hemisected Man and Woman.jpg|thumb|upright=0.8|right|"Coition of a Hemisected Man and Woman" (c. 1492), an interpretation of what happens inside the body during coitus, by [[Leonardo da Vinci]]]]
Natural human reproduction involves penile–vaginal penetration,<ref name="Evan Jones">{{cite book |title=Human Reproductive Biology |isbn =978-0-12-088465-0 |publisher=[[Academic Press]] |year=2006 |pages=[https://archive.org/details/humanreproductiv0000jone_l0u3/page/205 205-206] |access-date=June 5, 2022 <!-- Coitus (sexual intercourse) --> |url=https://archive.org/details/humanreproductiv0000jone_l0u3|url-access=registration|author1=Richard Evan Jones |author2=Kristin H. López }}</ref> during which [[semen]], containing male gametes known as [[Spermatozoon|sperm]] cells or spermatozoa, is [[ejaculated]] through the penis into the vagina. The sperm passes through the [[vaginal vault]], [[cervix]] and into the [[uterus]], and then into the [[fallopian tube]]s. Millions of sperm are ejaculated to increase the chances of [[Human fertilization|fertilization]] (see [[Human sperm competition|sperm competition]]), but only one is sufficient to fertilize an egg or [[ovum]]. When a fertile ovum from the female is present in the fallopian tubes, the male gamete fertilizes the ovum, forming a new [[embryo]]. [[Pregnancy]] begins after the fertilized ovum is implanted in the lining of the uterus (the [[endometrium]]).<ref name="Evan Jones"/><ref name="Starr3">{{cite book| author = Cecie Starr|author2= Beverly McMillan|title = Human Biology| publisher = [[Cengage Learning]] | year = 2015 | page = 339| access-date = December 27, 2017 |isbn = 978-1-305-44594-9| url =https://books.google.com/books?id=lS5-BAAAQBAJ&pg=PT339}}</ref>

[[Pregnancy rate#Pregnancy rate for sexual intercourse|Pregnancy rates for sexual intercourse]] are highest during the [[menstrual cycle]] time from some five days before until approximately one day after ovulation (this is sometimes called the [[fertile window]]).<ref name=":1">{{Cite journal |last1=Gibbons |first1=Tatjana |last2=Reavey |first2=Jane |last3=Georgiou |first3=Ektoras X |last4=Becker |first4=Christian M |date=September 15, 2023 |editor-last=Cochrane Gynaecology and Fertility Group |title=Timed intercourse for couples trying to conceive |journal=Cochrane Database of Systematic Reviews |language=en |volume=2023 |issue=9 |pages=CD011345 |doi=10.1002/14651858.CD011345.pub3|pmid=37709293 |pmc=10501857 }}</ref> For optimal pregnancy chance, there are recommendations of [[vaginal intercourse]] every one or two days,<ref>{{cite web|url=https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/how-to-get-pregnant/art-20047611|title=How to get pregnant|website=[[Mayo Clinic]]|date=November 2, 2016|access-date=February 16, 2018}}</ref> or every two or three days.<ref>{{cite web|url=https://www.nice.org.uk/guidance/cg156/ifp/chapter/trying-for-a-baby|title=Fertility problems: assessment and treatment, Clinical guideline [CG156]|website=[[National Institute for Health and Care Excellence]]|date=February 20, 2013 |access-date=February 16, 2018}} Published date: February 2013. Last updated: September 2017</ref> Some people who are trying to conceive may choose to time vaginal intercourse with the fertile window, a practice that is sometimes called 'timed intercourse'.<ref name=":1" /> Timed intercourse using urine tests that predict ovulation may help improve the rate of pregnancy and live births for some couples trying to conceive such as those who have been trying for less than 12-months and who are under 40 years old, however, it is not clear from medical evidence if timed intercourse improves the rate of ultra-sound confirmed pregnancies and it is also not clear if timed intercourse has an effect on a person's level of stress or their quality of life.<ref name=":1" /> Studies have shown no significant difference between different [[sex positions]] and pregnancy rate, as long as it results in [[ejaculation]] into the vagina.<ref name=americanpregnancy>{{cite web|url=http://americanpregnancy.org/getting-pregnant-ebook/p7M7O0q1c71703C/gettingpregnant.pdf|title=The Essential Guide to Getting Pregnant|website=American Pregnancy Association|author=Philip B. Imler & David Wilbanks|date=November 2019|access-date=February 16, 2018|archive-date=June 1, 2018|archive-url=https://web.archive.org/web/20180601033115/http://americanpregnancy.org/getting-pregnant-ebook/p7M7O0q1c71703C/gettingpregnant.pdf|url-status=dead}}</ref>

When a [[sperm donor]] has sexual intercourse with a woman who is not his partner and for the sole purpose of impregnating the woman, this may be known as natural [[insemination]], as opposed to [[artificial insemination]]. Artificial insemination is a form of [[assisted reproductive technology]], which are methods used to achieve pregnancy by artificial or partially artificial means.<ref name="Bobick and Balaban">{{cite book|author1=James Bobick |author2=Naomi Balaban |title=The Handy Anatomy Answer Book|isbn=978-1-57859-328-6|publisher=[[Visible Ink Press]]|year=2008|pages=306–307|access-date=August 21, 2013|url=https://books.google.com/books?id=LBI2Sg2yYMoC&pg=PA305}}</ref> For artificial insemination, [[sperm donors]] may donate their sperm through a [[sperm bank]], and the insemination is performed with the express intention of attempting to impregnate the female; to this extent, its purpose is the medical equivalent of sexual intercourse.<ref name="Sharma">{{cite book|author=R.K. Sharma|title=Concise Textbook Of Forensic Medicine & Toxicology|isbn=978-81-312-1145-8|publisher=[[Elsevier|Elsevier India]]|year=2007|pages=113–116|access-date=October 13, 2013|url=https://books.google.com/books?id=_zAwlKX_zNwC&pg=PA113}}</ref><ref name="O'Toole">{{cite book|author=Mosby, Marie T. O'Toole|title=Mosby's Medical Dictionary|isbn=978-0-323-11258-1|publisher=[[Elsevier Health Sciences]]|year=2013|page=138|access-date=October 13, 2013|url=https://books.google.com/books?id=aW0zkZl0JgQC&pg=PA138}}</ref> [[Intracervical insemination|ICI]] insemination, which involves the deposit of (usually) raw semen in the vagina of a woman, is in effect a substitute for intercourse and is often contrasted with 'normal intercourse' in this context. Reproductive methods also extend to gay and lesbian couples. For gay male pairings, there is the option of [[Surrogacy|surrogate]] pregnancy; for lesbian couples, there is donor insemination in addition to choosing surrogate pregnancy.<ref name="Berkowitz">{{cite journal |vauthors=Berkowitz D, Marsiglio W | s2cid = 38458107 | year = 2007 | title = Gay Men: Negotiating Procreative, Father, and Family Identities | journal = Journal of Marriage and Family | volume = 69 | issue = 2| pages = 366–381 | doi = 10.1111/j.1741-3737.2007.00371.x }}</ref><ref name="Burda">{{Cite book| author = Joan M. Burda| title = Gay, lesbian, and transgender clients: a lawyer's guide | publisher = [[American Bar Association]]| year = 2008 |pages =69–74| isbn = 978-1-59031-944-4|access-date=July 28, 2011|url=https://books.google.com/books?id=QdzB1f8Y8Q8C&pg=PA69}}</ref> Some women use artificial insemination to become [[single mothers by choice]].<ref>{{cite journal |last1=Fiese |first1=Barbara |title=Single Mothers by Choice: Mother–Child Relationships and Children's Psychological Adjustment |journal=J Fam Psychol |date=2016 |volume=30 |issue=4 |pages=409–418 |doi=10.1037/fam0000188 |pmid=26866836 |pmc=4886836 }}</ref>

===Safe sex and birth control===
{{See also|Comparison of birth control methods}}
There are a variety of [[safe sex]] methods that are practiced by heterosexual and same-sex couples, including non-penetrative sex acts,<ref name="Kumar"/><ref name="Durham">{{cite book|title=The Person With HIV/AIDS: Nursing Perspectives|edition=3rd|isbn = 978-81-223-0004-8|publisher=[[Springer Publishing Company]]|year=2000|page=103|access-date=January 29, 2012|url=https://books.google.com/books?id=WSCQ4L8kSXsC&pg=PA103|author1=Jerry D. Durham |author2=Felissa R. Lashley }}</ref> and heterosexual couples may use oral or anal sex (or both) as a means of birth control.<ref name="Crooks">{{cite book | title = Our Sexuality | publisher = [[Cengage Learning]] | year = 2010 | pages = 286–289 | access-date = August 30, 2012 |isbn = 978-0-495-81294-4| url = https://books.google.com/books?id=MpRnPtmdRVwC&pg=PA286|quote=Noncoital forms of sexual intimacy, which have been called outercourse, can be a viable form of birth control. Outercourse includes all avenues of sexual intimacy other than penile–vaginal intercourse, including kissing, touching, mutual masturbation, and oral and anal sex. |author1=Robert Crooks |author2=Karla Baur }}</ref><ref>{{cite journal |vauthors=Feldmann J, Middleman AB | title = Adolescent sexuality and sexual behavior | journal = Current Opinion in Obstetrics and Gynecology | volume = 14 | issue = 5 | pages = 489–493 | year = 2002 | pmid = 12401976 | doi=10.1097/00001703-200210000-00008| s2cid = 29206790 }}</ref> However, pregnancy can still occur with anal sex or other forms of sexual activity if the penis is near the vagina (such as during [[intercrural sex]] or other [[genital-genital rubbing]]) and its sperm is deposited near the vagina's entrance and travels along the vagina's lubricating fluids; the risk of pregnancy can also occur without the penis being near the vagina because sperm may be transported to the vaginal opening by the vagina coming in contact with fingers or other non-genital body parts that have come in contact with semen.<ref>{{cite book|last=Thomas|first=R. Murray|title=Sex and the American teenager seeing through the myths and confronting the issues|year=2009|publisher=[[Rowman & Littlefield Education]]|location=Lanham, Md.|isbn=978-1-60709-018-2|page=81|url=https://books.google.com/books?id=gM9EFgsJHyoC&pg=PA81|access-date=October 21, 2015}}</ref><ref>{{cite book|last=Edlin|first=Gordon|title=Health & Wellness.|year=2012|publisher=[[Jones & Bartlett Learning]]|isbn=978-1-4496-3647-0|page=213|url=https://books.google.com/books?id=csGk6j5rlN0C&pg=PA213|access-date=October 21, 2015}}</ref>

Safe sex is a relevant [[harm reduction]] philosophy<ref name="Mercer">{{cite journal | vauthors = Chin HB, Sipe TA, Elder R, Mercer SL, Chattopadhyay SK, Jacob V, Wethington HR, Kirby D, Elliston DB, Griffith M, Chuke SO, Briss SC, Ericksen I, Galbraith JS, Herbst JH, Johnson RL, Kraft JM, Noar SM, Romero LM, Santelli J | title = The Effectiveness of Group-Based Comprehensive Risk-Reduction and Abstinence Education Interventions to Prevent or Reduce the Risk of Adolescent Pregnancy, Human Immunodeficiency Virus, and Sexually Transmitted Infections | journal = American Journal of Preventive Medicine | volume = 42 | issue = 3 | pages = 272–294 | year = 2012 | pmid = 22341164 | doi = 10.1016/j.amepre.2011.11.006 | url = http://www.ajpmonline.org/article/S0749-3797(11)00906-8/abstract | access-date = July 23, 2013 | archive-date = January 2, 2020 | archive-url = https://web.archive.org/web/20200102180246/https://www.ajpmonline.org/article/S0749-3797(11)00906-8/abstract | url-status = dead }}</ref> and [[condom]]s are used as a form of safe sex and contraception. Condoms are widely recommended for the prevention of [[sexually transmitted infections]] (STIs).<ref name="Mercer"/> According to reports by the [[National Institutes of Health]] (NIH) and [[World Health Organization]] (WHO), correct and consistent use of latex condoms reduces the risk of [[HIV/AIDS]] transmission by approximately 85–99% relative to risk when unprotected.<ref>{{cite conference|author=National Institute of Allergy and Infectious Diseases |author-link=National Institute of Allergy and Infectious Diseases |author2=National Institutes of Health, Department of Health and Human Services |title=Workshop Summary: Scientific Evidence on Condom Effectiveness for Sexually Transmitted Disease (STD) Prevention |pages=13–15 |date=July 20, 2001 |location=Hyatt Dulles Airport, Herndon, Virginia |url=http://www3.niaid.nih.gov/about/organization/dmid/PDF/condomReport.pdf |archive-url=https://web.archive.org/web/20100307132024/http://www3.niaid.nih.gov/about/organization/dmid/PDF/condomReport.pdf |archive-date=March 7, 2010 |access-date=March 20, 2009 |url-status=dead}}</ref><ref name="WHO condoms">{{cite web|title=Effectiveness of male latex condoms in protecting against pregnancy and sexually transmitted infections|publisher=[[World Health Organization]]|year=2000|access-date=July 23, 2013|url=https://www.who.int/mediacentre/factsheets/fs243/en/index.html|archive-url=https://web.archive.org/web/20100509064325/http://www.who.int/mediacentre/factsheets/fs243/en/index.html |archive-date=May 9, 2010 }}</ref> Condoms are rarely used for oral sex and there is significantly less research on behaviors with regard to condom use for anal and oral sex.<ref name="Kumar 2">{{cite book|title=Sexually Transmitted Infections E book| author = Bhushan Kumar, Somesh Gupta| publisher = [[Elsevier Health Sciences]] | year = 2014 | page = 122 |isbn = 978-81-312-2978-1| url =https://books.google.com/books?id=kQ9tAwAAQBAJ}}</ref> The most effective way to avoid sexually transmitted infections is to [[Sexual abstinence|abstain]] from sexual intercourse, especially vaginal, anal, and oral sexual intercourse.<ref name="Mercer"/>

Decisions and options concerning birth control can be affected by cultural reasons, such as religion, [[gender role]]s or [[folklore]].<ref name="Hales2">{{cite book | title = An Invitation to Health: Choosing to Change| publisher = [[Cengage Learning]]| year = 2010 | pages = 301–302| access-date = March 30, 2013 |isbn = 978-0-538-73655-8| url = https://books.google.com/books?id=yPa0LZXizO4C&pg=PA301 | author = Dianne Hales}}</ref> In the predominantly [[Catholic]] countries Ireland, Italy, and the Philippines, [[fertility awareness]] and the [[Calendar-based contraceptive methods|rhythm method]] are emphasized while disapproval is expressed with regard to other contraceptive methods.<ref name="Hales"/> Worldwide, [[Sterilization (medicine)|sterilization]] is a more common birth control method,<ref name="Hales"/> and use of the [[intrauterine device]] (IUD) is the most common and effective way of reversible contraception.<ref name="Hales"/><ref name=Winner2012>{{cite journal |vauthors=Winner B, Peipert JF, Zhao Q, Buckel C, Madden T, Allsworth JE, Secura GM | title = Effectiveness of long-acting reversible contraception | journal = N. Engl. J. Med. | volume = 366 | issue = 21 | pages = 1998–2007 | year = 2012 | pmid = 22621627 | doi = 10.1056/NEJMoa1110855 | s2cid = 16812353 | url = https://digitalcommons.wustl.edu/cgi/viewcontent.cgi?article=3776&context=open_access_pubs | doi-access = free }}</ref> Conception and contraception are additionally a life-and-death situation in [[developing countries]], where one in three women give birth before age 20; however, 90% of [[unsafe abortion]]s in these countries could be prevented by effective contraception use.<ref name="Hales"/>

The [[National Survey of Sexual Health and Behavior]] (NSSHB) indicated in 2010 that "1 of 4 acts of vaginal intercourse are condom-protected in the U.S. (1 in 3 among singles)," that "condom use is higher among black and Hispanic Americans than among white Americans and those from other racial groups," and that "adults using a condom for intercourse were just as likely to rate the sexual extent positively in terms of arousal, pleasure and orgasm than when having intercourse without one".<ref name="NSSHB">{{cite journal |title=Findings from the National Survey of Sexual Health and Behavior, Centre for Sexual Health Promotion, Indiana University |journal= [[The Journal of Sexual Medicine]] |volume=7 |issue=Supplement 5 |page=4 |year=2010 |access-date=March 4, 2011|url=http://www.kinseyinstitute.org/resources/FAQ.html}}</ref>

===Prevalence===
Penile–vaginal penetration is the most common form of sexual intercourse.<ref name="Alters"/><ref name="Carroll"/> Studies indicate that most heterosexual couples engage in vaginal intercourse nearly every sexual encounter.<ref name="Carroll"/> The National Survey of Sexual Health and Behavior (NSSHB) reported in 2010 that vaginal intercourse is "the most prevalent sexual behavior among men and women of all ages and ethnicities".<ref name="Carroll"/> Clint E. Bruess et al. stated that it "is the most frequently studied behavior" and is "often the focus of sexuality education programming for youth."<ref name="Bruess">{{cite book| author = Clint E. Bruess| author2 = Elizabeth Schroeder|title = Sexuality Education Theory and Practice| publisher = [[Jones & Bartlett Publishers]] | year = 2013 | page = 152 | access-date = December 5, 2014 |isbn = 978-1-4496-4928-9| url =https://books.google.com/books?id=WWFW6-kkAVoC&pg=PA152}}</ref> Weiten et al. said that it "is the most widely endorsed and practiced sexual act in our society."<ref name="Weiten3"/>

Regarding oral or anal intercourse, the CDC stated in 2009, "Studies indicate that oral sex is commonly practiced by sexually active male-female and same-gender couples of various ages, including adolescents."<ref name="CDC, oral sex"/> Oral sex is significantly more common than anal sex.<ref name="Weiten3"/><ref name="Aggleton 1"/> The 2010 NSSHB study reported that vaginal intercourse was practiced more than insertive anal intercourse among men, but that 13% to 15% of men aged 25 to 49 practiced insertive anal intercourse. Receptive anal intercourse was infrequent among men, with approximately 7% of men aged 14 to 94 years old having said that they were a receptive partner during anal intercourse. The study said that fewer women reported engaging in anal sex than other partnered sexual behaviors. It was estimated that 10% to 14% of women aged 18 to 39 years old practiced anal sex in the past 90 days, and that most of the women who engage in anal sex said they practiced it once a month or a few times a year.<ref name="Carroll"/>

===={{anchor|sexarche}}Age at first intercourse====
The prevalence of sexual intercourse has been compared cross-culturally. In 2003, Michael Bozon of the French [[Institut national d'études démographiques]] conducted a cross-cultural study titled "At what age do women and men have their first sexual intercourse?" In the first group of the contemporary cultures he studied, which included [[sub-Saharan Africa]] (listing [[Mali]], [[Senegal]] and [[Ethiopia]]), the data indicated that the age of men at sexual initiation in these societies is at later ages than that of women, but is often extra-marital; the study considered the [[Indian subcontinent]] to also fall into this group, though data was only available from [[Nepal]].<ref name="Bozon">{{cite journal |last=Bozon |first=Michael |year=2003 |title=At what age do women and men have their first sexual intercourse? World comparisons and recent trends |journal=Population and Societies |volume=391 |pages=1–4 |url=https://www.ined.fr/fichier/s_rubrique/247/english_391.en.pdf |url-status=dead |archive-url=https://web.archive.org/web/20160304091955/https://www.ined.fr/fichier/s_rubrique/247/english_391.en.pdf |archive-date=March 4, 2016}}</ref><ref name="Caselli">{{cite book| author = Graziella Caselli| author2 = Guillaume Wunsch| author3 = Daniel Courgeau| author4 = Jacques Vallin| title = Demography&nbsp;– Analysis and Synthesis: A Treatise in Population| publisher = [[Academic Press]] | year = 2005 | pages = 490–501 | access-date = September 6, 2013 |isbn = 978-0-12-765660-1| url=https://books.google.com/books?id=nmgNXoiAiU4C&pg=PA491}}</ref>

In the second group, the data indicated families encouraged daughters to delay marriage, and to abstain from sexual activity before that time. However, sons are encouraged to gain experience with older women or prostitutes before marriage. Age of men at sexual initiation in these societies is at lower ages than that of women; this group includes [[southern Europe|south European]] and Latin cultures (Portugal, Greece and Romania are noted) and such from [[Latin America]] (Brazil, [[Chile]], and the [[Dominican Republic]]). The study considered many Asian societies to also fall into this group, although matching data was only available from [[Thailand]].<ref name="Bozon"/><ref name="Caselli"/>

In the third group, age of men and women at sexual initiation was more closely matched; there were two sub-groups, however. In non-Latin, Catholic countries (Poland and [[Lithuania]] are mentioned), age at sexual initiation was higher, suggesting later marriage and reciprocal valuing of male and female virginity. The same pattern of late marriage and reciprocal valuing of virginity was reflected in [[Singapore]] and [[Sri Lanka]]. The study considered China and Vietnam to also fall into this group, though data were not available.<ref name="Bozon"/><ref name="Caselli"/> In northern and eastern European countries, age at sexual initiation was lower, with both men and women involved in sexual intercourse before any union formation; the study listed Switzerland, Germany and the Czech Republic as members of this group.<ref name="Bozon"/><ref name="Caselli"/>

Concerning United States data, tabulations by the [[National Center for Health Statistics]] report that the age of first sexual intercourse was 17.1 years for both males and females in 2010.<ref name="CDC abc_list_s">{{cite web|title=Key Statistics from the National Survey of Family Growth|access-date=February 9, 2013|publisher=[[Centers for Disease Control and Prevention]] (CDC)|url=https://www.cdc.gov/nchs/nsfg/abc_list_s.htm}}</ref> The CDC stated that 45.5 percent of girls and 45.7 percent of boys had engaged in sexual activity by 19 in 2002; in 2011, reporting their research from 2006 to 2010, they stated that 43% of American unmarried teenage girls and 42% of American unmarried teenage boys have ever engaged in sexual intercourse.<ref name="CDC statistics">{{cite web|title=Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2006–2010 National Survey of Family Growth|access-date=December 26, 2012|publisher=[[Centers for Disease Control and Prevention]] (CDC)|url=https://www.cdc.gov/nchs/data/series/sr_23/sr23_031.pdf}}</ref> The CDC also reports that American girls will most likely lose their virginity to a boy who is 1 to 3 years older than they are.<ref name="CDC statistics"/> Between 1988 and 2002, the percentage of people in the U.S. who had sexual intercourse between the ages of 15 and 19 fell from 60 to 46 percent for never-married males, and from 51 to 46 percent for never-married females.<ref name="CDC sr23_024">{{cite web|title=Teenagers in the United States: Sexual Activity, Contraceptive Use, and Childbearing, 2002|access-date=February 9, 2013|publisher=[[Centers for Disease Control and Prevention]] (CDC)|url=https://www.cdc.gov/nchs/data/series/sr_23/sr23_024.pdf}}</ref>

==Health effects==

==={{anchor|Benefits}}Benefits===
In humans, sexual intercourse and sexual activity in general have been reported as having health benefits as varied as increased [[immune system|immunity]] by increasing the body's production of [[antibodies]] and subsequent lower [[blood pressure]],<ref name="Steptoe">{{cite book| author = Andrew Steptoe| author2 = Kenneth Freedland| author3 = J. Richard Jennings| author4 = Maria M. Llabre| author5 = Stephen B Manuck| author6 = Elizabeth J. Susman|author-link=Andrew Steptoe |author5-link=Stephen Manuck |title =Handbook of Behavioral Medicine: Methods and Applications| publisher = [[Springer Science & Business Media]] | year = 2010 | pages = 60–61 | access-date = December 7, 2014 |isbn = 978-0-387-09488-5| url =https://books.google.com/books?id=Si9TtI5AGIEC&pg=PA60}}</ref><ref name="Hornstein">{{cite book| author = Theresa Hornstein| author2 = Jeri Schwerin|title =Biology of Women| publisher = [[Cengage Learning]] | year = 2012 | page = 205 | access-date = December 7, 2014 |isbn = 978-1-285-40102-7| url =https://books.google.com/books?id=ibgKAAAAQBAJ&pg=PA205}}</ref> and decreased risk of [[prostate cancer]].<ref name="Steptoe"/> Sexual intimacy and orgasms increase levels of the hormone [[oxytocin]] (also known as "the love hormone"), which can help people bond and build trust.<ref name="Hornstein"/><ref name="Sigelman">{{cite book| author = Carol Sigelman| author2 = Elizabeth Rider|title =Life-Span Human Development| publisher = [[Cengage Learning]] | year = 2011 | page = 452 | access-date = December 7, 2014 |isbn = 978-1-111-34273-9| url =https://books.google.com/books?id=8smBuRecmDsC&pg=PT480}}</ref> Oxytocin is believed to have a more significant impact on women than on men, which may be why women associate sexual attraction or sexual activity with romance and love more than men do.<ref name="Freberg"/> A long-term study of 3,500 people between ages 18 and 102 by clinical [[neuropsychologist]] David Weeks indicated that, based on impartial ratings of the subjects' photographs, sex on a regular basis is associated with people looking significantly chronologically younger. However this does not imply causality.<ref>{{cite book|last=Northrup|first=Christiane|author-link=Christiane Northrup|title=Women's Bodies, Women's Wisdom: Creating Physical and Emotional Health and Healing|year=2010|publisher=Bantam|isbn=978-0-553-80793-6|page=232|url=https://books.google.com/books?id=V9S3keMnie8C&pg=PA232|access-date=October 21, 2015}}</ref>

Vaginal intercourse for the first time increases vaginal immune activity.<ref name="10.7554/eLife.78565">{{cite journal |last1=Hughes |first1=Sean M |last2=Levy |first2=Claire N |last3=Calienes |first3=Fernanda L |last4=Martinez |first4=Katie A |last5=Selke |first5=Stacy |last6=Tapia |first6=Kenneth |last7=Chohan |first7=Bhavna H |last8=Oluoch |first8=Lynda |last9=Kiptinness |first9=Catherine |last10=Wald |first10=Anna |last11=Ghosh |first11=Mimi |last12=Hardy |first12=Liselotte |last13=Ngure |first13=Kenneth |last14=Mugo |first14=Nelly R |last15=Hladik |first15=Florian |last16=Roxby |first16=Alison C |title=Starting to have sexual intercourse is associated with increases in cervicovaginal immune mediators in young women: a prospective study and meta-analysis |journal=eLife |date=October 25, 2022 |volume=11 |pages=e78565 |doi=10.7554/eLife.78565 |pmid=36281966 |pmc=9596159 |doi-access=free }}</ref>

===Risks{{anchor|General risks}}===
[[Sexually transmitted infection]]s (STIs) are [[bacteria]], [[virus]]es or [[parasites]] that are [[Transmission (medicine)|spread]] by sexual contact, especially vaginal, anal, or oral intercourse, or [[unprotected sex]].<ref name="Hoeger">{{cite book|vauthors=Hoeger W, HS, FA, HC|title=Principles and Labs for Fitness and Wellness| publisher = [[Cengage Learning]] | year = 2016 | pages = 538–540|isbn = 978-1-337-09997-4| url =https://books.google.com/books?id=wdq5DQAAQBAJ}}</ref><ref name=Women2017>{{Cite web|url=https://www.womenshealth.gov/a-z-topics/sexually-transmitted-infections|title=Sexually transmitted infections|website=womenshealth.gov|language=en|access-date=December 8, 2017|date=February 22, 2017}}{{PD-notice}}</ref> Oral sex is less risky than vaginal or anal intercourse.<ref name="Gulanick">{{cite book|vauthors=Gulanick M, Myers JL |title=Nursing Care Plans - E-Book: Diagnoses, Interventions, and Outcomes| publisher=[[Elsevier Health Sciences]] |year=2016 |page=725|isbn=978-0-323-42810-1| url=https://books.google.com/books?id=NK2ADQAAQBAJ}}</ref> Many times, STIs initially do not cause symptoms, increasing the risk of unknowingly passing the infection on to a sex partner or others.<ref>{{cite book|vauthors=Murray PR, Rosenthal KS, Pfaller MA|title=Medical microbiology|date=2013|publisher=Mosby|location=St. Louis, MO|isbn=978-0-323-08692-9 |page=418|edition=7th|url=https://books.google.com/books?id=RBEVsFmR2yQC&pg=PA418 |url-status=live |archive-url=https://web.archive.org/web/20151201070705/https://books.google.com/books?id=RBEVsFmR2yQC&pg=PA418 |archive-date=December 1, 2015}}</ref><ref>{{cite book|last1=Goering|first1=Richard V.|title=Mims' medical microbiology |date=2012 |publisher=Saunders|location=Edinburgh|isbn=978-0-7234-3601-0 |page=245 |edition=5th |url=https://books.google.com/books?id=pzQayLEQ5mQC&pg=PA245}}</ref>

There are 19 million new cases of sexually transmitted infections every year in the U.S.,<ref>{{cite web|title=STD Trends in the United States: 2010 National Data for Gonorrhea, Chlamydia, and Syphilis |url=https://www.cdc.gov/std/stats10/trends.htm |publisher=[[Centers for Disease Control and Prevention]] |url-status=dead |archive-url=https://web.archive.org/web/20120326175627/https://www.cdc.gov/std/stats10/trends.htm |archive-date=March 26, 2012 |access-date=September 23, 2023}}</ref> and, in 2005, the World Health Organization (WHO) estimated that 448 million people aged 15–49 were infected per year with curable STIs (such as [[syphilis]], [[gonorrhea]] and [[chlamydia]]).<ref name="WHO 2015">{{cite web| title=Sexually transmitted infections (STIs)|publisher=World Health Organization| url =https://www.who.int/mediacentre/factsheets/fs110/en/| access-date = June 20, 2015}}</ref> Some STIs can cause a [[genital ulcer]]; even if they do not, they increase the risk of both acquiring and passing on HIV up to ten-fold.<ref name="WHO 2015"/> [[Hepatitis B]] can also be transmitted through sexual contact.<ref>[https://www.cdc.gov/hepatitis/HBV/HBVfaq.htm#treatment CDC Hepatitis B Information for Health Professionals] Accessed May 27, 2010</ref> Globally, there are about 257 million chronic carriers of hepatitis B.<ref>{{cite web|title=Hepatitis B|url=https://www.who.int/news-room/fact-sheets/detail/hepatitis-b |publisher=[[World Health Organization]] |date=July 18, 2018}}</ref> HIV is one of the world's leading infectious killers; in 2010, approximately 30 million people were estimated to have died because of it since the beginning of the epidemic. Of the 2.7 million new [[Epidemiology of HIV/AIDS|HIV infections]] estimated to occur worldwide in 2010, 1.9 million (70%) were in [[HIV/AIDS in Africa|Africa]]. The World Health Organization also stated that the "estimated 1.2 million Africans who died of HIV-related illnesses in 2010 comprised 69% of the global total of 1.8 million deaths attributable to the epidemic."<ref name=WHO-HIV>{{cite web|title=HIV/AIDS|publisher=[[World Health Organization]] |url=https://www.who.int/gho/hiv/en/index.html|access-date=September 15, 2012}}</ref> It is [[Diagnosis of HIV/AIDS|diagnosed by blood tests]], and while no cure has been found, it can be controlled by management [[Management of HIV/AIDS|through antiretroviral drugs for the disease]], and patients can enjoy healthy and productive lives.<ref name=WHO-2012>{{cite web|title=HIV/AIDS|url=https://www.who.int/mediacentre/factsheets/fs360/en/index.html|work=Fact sheet N° 360|publisher=[[World Health Organization]]|access-date=September 8, 2012|date=July 2012}}</ref>

In cases where infection is suspected, early medical intervention is highly beneficial in all cases. The CDC stated "the risk of HIV transmission from an infected partner through oral sex is much less than the risk of HIV transmission from anal or vaginal sex," but that "measuring the exact risk of HIV transmission as a result of oral sex is very difficult" and that this is "because most sexually active individuals practice oral sex in addition to other forms of sex, such as vaginal or anal sex, when transmission occurs, it is difficult to determine whether it occurred as a result of oral sex or other more risky sexual activities". They added that "several co-factors may increase the risk of HIV transmission through oral sex"; this includes ulcers, [[Bleeding on probing|bleeding gums]], genital sores, and the presence of other STIs.<ref name="CDC, oral sex"/>

In 2005, the World Health Organization estimated that 123 million women become pregnant worldwide each year, and around 87 million of those pregnancies or 70.7% are unintentional. Approximately 46 million pregnancies per year reportedly end in induced [[abortion]].<ref>{{cite web|title=Not Every Pregnancy is Welcome|url=https://www.who.int/whr/2005/chapter3/en/index3.html|archive-url=https://web.archive.org/web/20050414233054/http://www.who.int/whr/2005/chapter3/en/index3.html|url-status=dead|archive-date=April 14, 2005|work=The world health report 2005&nbsp;– make every mother and child count|publisher=[[World Health Organization]]|access-date=December 6, 2011}}</ref> Approximately 6 million U.S. women become pregnant per year. Out of known pregnancies, two-thirds result in live births and roughly 25% in abortions; the remainder end in miscarriage. However, many more women become pregnant and miscarry without even realizing it, instead mistaking the miscarriage for an unusually heavy [[menstruation]].<ref name="Guttmacher 0">{{cite web|title=Get "In the Know": 20 Questions About Pregnancy, Contraception and Abortion |publisher=[[Guttmacher Institute]] |year=2005 |access-date=March 4, 2011 |url=http://www.guttmacher.org/in-the-know/index.html |url-status=deviated |archive-url=https://web.archive.org/web/20091223093547/http://www.guttmacher.org/in-the-know/index.html |archive-date=December 23, 2009 }}</ref> The U.S. [[teenage pregnancy]] rate fell by 27 percent between 1990 and 2000, from 116.3 pregnancies per 1,000 girls aged 15–19 to 84.5. This data includes live births, abortions, and fetal losses. Almost 1 million American teenage women, 10% of all women aged 15–19 and 19% of those who report having had intercourse, become pregnant each year.<ref name="Ventura">{{cite web|author=Ventura, SJ|author2=Abma, JC|author3=Mosher, WD|author4=Henshaw, S.|name-list-style=amp|title=Estimated pregnancy rates for the United States, 1990–2000: An Update. National Vital Statistics Reports, 52 (23)|publisher=[[Centers for Disease Control and Prevention]]|date=November 16, 2007|access-date=March 4, 2011|url=https://www.cdc.gov/nchs/data/nvsr/nvsr52/nvsr52_23.pdf}}</ref>

Sexual activity can increase the expression of a [[gene transcription]] factor called [[ΔFosB]] (delta FosB) in the [[nucleus accumbens|brain's reward center]];<ref name="ΔFosB reward">{{cite journal |vauthors=Blum K, Werner T, Carnes S, Carnes P, Bowirrat A, Giordano J, Oscar-Berman M, Gold M | title = Sex, drugs, and rock 'n' roll: hypothesizing common mesolimbic activation as a function of reward gene polymorphisms | journal = Journal of Psychoactive Drugs | volume = 44 | issue = 1 | pages = 38–55 | year = 2012 | pmid = 22641964 | pmc = 4040958 | doi = 10.1080/02791072.2012.662112}}</ref><ref name="Natural and drug addictions">{{cite journal | author = Olsen CM | title = Natural rewards, neuroplasticity, and non-drug addictions | journal = Neuropharmacology | volume = 61 | issue = 7 | pages = 1109–1122 |date=December 2011 | pmid = 21459101 | pmc = 3139704 | doi = 10.1016/j.neuropharm.2011.03.010 }}</ref><ref name="Amph and sex addiction"><!--Supplemental primary source-->{{cite journal |vauthors=Pitchers KK, Vialou V, [[Eric J. Nestler|Nestler EJ]], Laviolette SR, Lehman MN, Coolen LM | title = Natural and drug rewards act on common neural plasticity mechanisms with ΔFosB as a key mediator | journal = J. Neurosci. | volume = 33 | issue = 8 | pages = 3434–42 |date=February 2013 | pmid = 23426671 | pmc = 3865508 | doi = 10.1523/JNEUROSCI.4881-12.2013 }}</ref> consequently excessively frequent engagement in sexual activity on a regular (daily) basis can lead to the overexpression of ΔFosB, inducing an addiction to sexual activity.<ref name="ΔFosB reward" /><ref name="Natural and drug addictions" /><ref name="Amph and sex addiction" /> [[Sexual addiction]] or [[hypersexuality]] is often considered an impulse control disorder or a behavioral addiction. It has been linked to atypical levels of dopamine, a neurotransmitter. This behavior is characterized by a fixation on sexual intercourse and disinhibition. It was proposed that this 'addictive behavior' be classified in [[DSM-5]] as an impulsive–compulsive behavioral disorder. Addiction to sexual intercourse is thought to be genetically linked. Those having an addiction to sexual intercourse have a higher response to visual sexual cues in the brain. Those seeking [[Psychiatric treatment|treatment]] will typically see a physician for pharmacological management and therapy.<ref name="Probstvan Eimeren2013">{{cite journal|last1=Probst |first1=Catharina C.|last2=van Eimeren|first2=Thilo|title=The Functional Anatomy of Impulse Control Disorders|journal=Current Neurology and Neuroscience Reports|volume=13|issue=10|pages=386|year=2013 |issn=1528-4042|doi=10.1007/s11910-013-0386-8|pmid=23963609|pmc=3779310}}</ref> One form of hypersexuality is [[Kleine–Levin syndrome]]. It is manifested by [[hypersomnia]] and hypersexuality and remains relatively rare.<ref name="GuilleminaultMiglis2014">{{cite journal|last1=Guilleminault|first1=Christian|last2=Miglis|first2=Mitchell|author1-link=Christian Guilleminault|title=Kleine-Levin syndrome: a review|journal=Nature and Science of Sleep|volume=6|pages=19–26|year=2014|issn=1179-1608|doi=10.2147/NSS.S44750|pmid=24470783|pmc=3901778 |doi-access=free }}</ref>

[[Death during consensual sex|Sexual activity can directly cause death]], particularly due to [[coronary circulation]] complications, which is sometimes called ''coital death,'' ''coital sudden death'' or ''coital coronary.''<ref name="Kahn, Fawcett"/><ref name="Kipshidze">{{Cite book|author= Nicolas Kipshidze|author2= Jawad Fareed|author3= Patrick W. Serruys|author4= Jeff Moses | title = Textbook of Interventional Cardiovascular Pharmacology| year = 2007 | publisher = [[CRC Press]] |page=505 | isbn = 978-0-203-46304-8| url=https://books.google.com/books?id=13g_niZy0usC&pg=PA505| access-date=October 21, 2015}}</ref><ref name="Dahabreh">{{cite journal|last=Dahabreh|first=Issa J. |title=Association of Episodic Physical and Sexual Activity With Triggering of Acute Cardiac Events. Systematic Review and Meta-analysis |journal=JAMA: The Journal of the American Medical Association|date=March 23, 2011|volume=305 |issue=12|pages=1225–33|doi=10.1001/jama.2011.336|pmid=21427375|pmc=5479331|quote=Acute cardiac events were significantly associated with episodic physical and sexual activity; this association was attenuated among persons with high levels of habitual physical activity.}}</ref> However, coital deaths are significantly rare.<ref name="Kipshidze"/> People, especially those who get little or no physical exercise, have a slightly increased risk of triggering a [[heart attack]] or [[sudden cardiac death]] when they engage in sexual intercourse or any vigorous physical exercise that is engaged in on a sporadic basis.<ref name="Dahabreh"/> Regular exercise reduces, but does not eliminate, the increased risk.<ref name="Dahabreh"/>

===Duration and genital complications===
{{see also|Intravaginal ejaculation latency time|Coitus reservatus}}

Sexual intercourse, when involving a male participant, often ends when the male has ejaculated, and thus the partner might not have time to reach [[orgasm]].<ref name="Wincze">{{Cite book|author= John Wincze | title = Enhancing Sexuality : A Problem-Solving Approach to Treating Dysfunction| year = 2009 | publisher = [[Oxford University Press]] |pages=56–60 | isbn = 978-0-19-971802-3| url=https://books.google.com/books?id=8YxbeHsgiGMC&pg=PA56}}</ref> In addition, [[premature ejaculation]] (PE) is common, and women often require a substantially longer duration of stimulation with a sexual partner than men do before reaching an orgasm.<ref name="Weiten, 2011" /><ref name="Porst">{{cite book |author = Hartmut Porst |author2 = Jacques Buvat|title =Standard Practice in Sexual Medicine| publisher = [[John Wiley & Sons]] | year = 2008|access-date=October 22, 2013 | page = 189|isbn = 978-1-4051-7872-3 |url=https://books.google.com/books?id=S4GJio79XOUC&pg=PA189}}</ref><ref name="Emmanuele">{{cite book|author1-link=Emmanuele A. Jannini|author = Emmanuele A. Jannini |author2 = Chris G. McMahon |author3 = Marcel D. Waldinger|title =Premature Ejaculation: From Etiology to Diagnosis and Treatment| publisher = [[Springer Publishing|Springer]] | year = 2012|access-date=October 22, 2013 | pages = 159–162|isbn = 978-88-470-2646-9 |url=https://books.google.com/books?id=iCXF3sWtgegC&pg=PA159}}</ref> Scholars, such as Weiten et al., state that "many couples are locked into the idea that orgasms should be achieved only through intercourse [penile-vaginal sex]," that "the word ''foreplay'' suggests that any other form of sexual stimulation is merely preparation for the 'main event'" and that "because women reach orgasm through intercourse less consistently than men," they are likelier than men to [[Fake orgasm|fake an orgasm]] to satisfy their sexual partners.<ref name="Weiten, 2011" />
[[File:Indiaerotic8.jpg|thumb|left|Painting of a couple (an Indian prince and lady) prolonging sexual intercourse]]
In 1991, scholars from the Kinsey Institute stated, "The truth is that the time between penetration and ejaculation varies not only from man to man, but from one time to the next for the same man." They added that the appropriate length for sexual intercourse is the length of time it takes for both partners to be mutually satisfied, emphasizing that [[Alfred Kinsey|Kinsey]] "found that 75 percent of men ejaculated within two minutes of penetration. But he didn't ask if the men or their partners considered two minutes mutually satisfying" and "more recent research reports slightly longer times for intercourse".<ref name="Reinisch">{{cite book | title = The Kinsey Institute New Report On Sex| publisher = [[Macmillan Publishers|Macmillan]] | year = 1991 | pages = 129–130| access-date = August 30, 2012 |isbn = 978-0-312-06386-3| url = https://books.google.com/books?id=KsW6wPiXEd0C&pg=PA129 |author1=June M. Reinisch |author2=Ruth Beasley |author1-link=June Reinisch }}</ref> A 2008 survey of Canadian and American [[sex therapists]] stated that the average time for heterosexual intercourse (coitus) was 7 minutes and that 1 to 2 minutes was too short, 3 to 7 minutes was adequate and 7 to 13 minutes desirable, while 10 to 30 minutes was too long.<ref name="Carroll"/><ref>{{cite journal |vauthors=Corty EW, Guardiani JM | title = Canadian and American Sex Therapists' Perceptions of Normal and Abnormal Ejaculatory Latencies: How Long Should Intercourse Last? | journal = The Journal of Sexual Medicine | volume = 5 | issue = 5 | pages = 1251–1256 | year = 2008 | pmid = 18331255 | doi = 10.1111/j.1743-6109.2008.00797.x }}</ref>

[[Anorgasmia]] is regular difficulty reaching orgasm after ample sexual stimulation, causing personal distress.<ref name="Bullough">{{cite book |author=Vern L Bullough |author2=Bonnie Bullough |author-link=Vern Bullough |author2-link=Bonnie Bullough | title = Human Sexuality: An Encyclopedia | publisher =[[Routledge]]|page=32|year = 2014|access-date=December 6, 2014| isbn = 978-1-135-82502-7 |url =https://books.google.com/books?id=-cqlAgAAQBAJ&pg=PA32}}</ref> This is significantly more common in women than in men,<ref name="Rosenthal">{{cite book |first=Martha |last= Rosenthal| title = Human Sexuality: From Cells to Society | publisher =[[Cengage Learning]]|year = 2012|page=150|access-date=October 22, 2013| isbn = 978-0-618-75571-4 |url =https://books.google.com/books?id=d58z5hgQ2gsC&pg=PT170}}</ref><ref name="Weiner2">{{cite book |author =Irving B. Weiner |author2 =George Stricker |author3 =Thomas A. Widiger |author3-link=Thomas Widiger|title =Handbook of Psychology, Clinical Psychology| publisher = [[John Wiley & Sons]] | year = 2012|access-date=October 22, 2013| pages = 172–175|isbn = 978-1-118-40443-0|url=https://books.google.com/books?id=A_NaK3cwQSsC&pg=PA172}}</ref> which has been attributed to the lack of [[sex education]] with regard to women's bodies, especially in [[Antisexualism|sex-negative]] cultures, such as clitoral stimulation usually being key for women to orgasm.<ref name="Weiner2"/> The physical structure of coitus favors penile stimulation over clitoral stimulation; the location of the clitoris then usually necessitates manual or oral stimulation in order for the woman to achieve orgasm.<ref name="Weiten, 2011"/> Approximately 25% of women report difficulties with orgasm,<ref name="Carroll"/> 10% of women have never had an orgasm,<ref name="Plotnik">{{cite book |author1=Rod Plotnik |author2=Haig Kouyoumdjian |title =Introduction to Psychology| publisher = [[Cengage Learning]] | year = 2010 | page = 344|isbn = 978-0-495-90344-4| quote= Inhibited female orgasm refers to a persistent delay or absence of orgasm after becoming aroused and excited. About 10% of women never reach orgasm...}}</ref> and 40% or 40–50% have either complained about sexual dissatisfaction or experienced difficulty becoming sexually aroused at some point in their lives.<ref name="Knoepp">{{cite journal |vauthors=Knoepp LR, Shippey SH, Chen CC, Cundiff GW, Derogatis LR, Handa VL | title = Sexual complaints, pelvic floor symptoms, and sexual distress in women over forty | journal = [[The Journal of Sexual Medicine]] | volume = 7 | issue = 11 | pages = 3675–82 | year = 2010 | pmid = 20704643 | pmc = 3163299 | doi = 10.1111/j.1743-6109.2010.01955.x }}</ref>

[[Vaginismus]] is involuntary tensing of the pelvic floor musculature, making coitus, or any form of penetration of the vagina, distressing, painful and sometimes impossible for women. It is a conditioned reflex of the pubococcygeus muscle, and is sometimes referred to as the ''PC muscle.'' Vaginismus can be hard to overcome because if a woman expects to experience pain during sexual intercourse, this can cause a muscle spasm, which results in painful sexual intercourse.<ref name="Weiner2"/><ref name="Ferri">{{cite book|author=Fred F. Ferri|title=Ferri's Clinical Advisor 2013,5 Books in 1, Expert Consult&nbsp;— Online and Print,1: Ferri's Clinical Advisor 2013|publisher=[[Elsevier Health Sciences]]|isbn=978-0-323-08373-7|year=2012|page=1134|access-date=November 29, 2014|url=https://books.google.com/books?id=OR3VERnvzzEC&pg=PA1134}}</ref> Treatment of vaginismus often includes both psychological and behavioral techniques, including the use of [[vaginal dilators]].<ref name="Goldman">{{cite book |author= Marlene B. Goldman |author2= Rebecca Troisi |author2-link=Rebecca J. Troisi |author3= Kathryn M. Rexrode| title = Women and Health | publisher =[[Academic Press]]|page=351|year = 2012|access-date=December 6, 2014| isbn = 978-0-12-384979-3 |url =https://books.google.com/books?id=mavb4v8w8bsC&pg=PA351}}</ref> Additionally, the use of [[Botox]] as a medical treatment for vaginismus has been tested and administered.<ref name="Comer">{{cite book |author= Ronald J. Comer| title = Fundamentals of Abnormal Psychology | publisher =[[Macmillan Publishers|Macmillan]]|page=338|year = 2010|access-date=December 6, 2014| isbn = 978-1-4292-1633-3 |url =https://books.google.com/books?id=y-FUzkLQ7GsC&pg=PA338}}</ref> Painful or uncomfortable sexual intercourse may also be categorized as [[dyspareunia]].<ref name="Goldman"/>

Approximately 40% of males reportedly have some form of [[erectile dysfunction]] (ED) or impotence, at least occasionally.<ref name="Schouten">{{cite journal |vauthors=Schouten BW, Bohnen AM, Groeneveld FP, Dohle GR, Thomas S, Bosch JL | title = Erectile dysfunction in the community: trends over time in incidence, prevalence, GP consultation and medication use—the Krimpen study: trends in ED | journal = J Sex Med | volume = 7 | issue = 7 | pages = 2547–53 | date = July 2010 | pmid = 20497307 | doi = 10.1111/j.1743-6109.2010.01849.x }}</ref> Premature ejaculation has been reported to be more common than erectile dysfunction, although some estimates suggest otherwise.<ref name="Porst"/><ref name="Emmanuele"/><ref name="Schouten" /> Due to various meanings of the disorder, estimates for the prevalence of premature ejaculation vary significantly more than for erectile dysfunction.<ref name="Porst" /><ref name="Emmanuele" /> For example, the [[Mayo Clinic]] states, "Estimates vary, but as many as 1 out of 3 men may be affected by [premature ejaculation] at some time."<ref name="Premature ejaculation">{{cite web|url=http://www.mayoclinic.com/health/premature-ejaculation/DS00578|title=Premature ejaculation|publisher=[[Mayo Clinic]].com|access-date=March 2, 2007}}</ref> Further, "Masters and Johnson speculated that premature ejaculation is the most common sexual dysfunction, even though more men seek therapy for erectile difficulties" and that this is because "although an estimated 15 percent to 20 percent of men experience difficulty controlling rapid ejaculation, most do not consider it a problem requiring help, and many women have difficulty expressing their sexual needs".<ref name="Reinisch"/> The [[American Urological Association]] (AUA) estimates that premature ejaculation could affect 21 percent of men in the United States.<ref name="auanet.org">{{cite web|title=Guideline on the pharmacologic management of premature ejaculation|publisher=[[American Urological Association]]|year=2004|access-date=October 12, 2013|url=http://www.auanet.org/common/pdf/education/clinical-guidance/Premature-Ejaculation.pdf|url-status=dead|archive-url=https://web.archive.org/web/20160303170443/http://www.auanet.org/common/pdf/education/clinical-guidance/Premature-Ejaculation.pdf|archive-date=March 3, 2016}}</ref>

For those whose impotence is caused by medical conditions, prescription drugs such as [[Viagra]], [[Cialis]], and [[Levitra]] are available. However, doctors caution against the unnecessary use of these drugs because they are accompanied by serious risks such as increased chance of heart attack.<ref name="Greenberg ED">{{cite book |author= Jerrold S Greenberg |author2= Clint E. Bruess |author3=Sara B. Oswalt | title = Exploring the Dimensions of Human Sexuality | publisher =[[Jones & Bartlett Publishers]]|page=633|year = 2010|access-date=December 8, 2014| isbn = 978-0-7637-9740-9 |url = https://books.google.com/books?id=6b36v8JHznIC&pg=PA633}}</ref> The [[selective serotonin reuptake inhibitor]] (SSRI) and antidepressant drug [[dapoxetine]] has been used to treat premature ejaculation.<ref name="Balon">{{cite book |author=Richard Balon |author2=Robert Taylor Segraves| title = Clinical Manual of Sexual Disorders | publisher =[[American Psychiatric Pub]]|page=292|year = 2009|access-date=December 6, 2014| isbn = 978-1-58562-905-3 |url =https://books.google.com/books?id=YuP3Hb0TMLQC&pg=PA292}}</ref> In clinical trials, those with PE who took dapoxetine experienced sexual intercourse three to four times longer before orgasm than without the drug.<ref name="Architectural Press">{{cite book| title = The Architects' Journal |volume=221 |issue=17–21 | publisher =[[Architectural Press]]|page=16|year = 2005|access-date=December 6, 2014|url =https://books.google.com/books?id=7HlNAAAAYAAJ&q=The+Architects%27+Journal,+Volume+221,+Issues+17-21}}</ref> Another ejaculation-related disorder is [[delayed ejaculation]], which can be caused as an unwanted side effect of antidepressant medications such as [[fluvoxamine]]; however, all SSRIs have ejaculation-delaying effects, and fluvoxamine has the least ejaculation-delaying effects.<ref name="Balon2">{{cite book |author= Richard Balon |author2= Robert Taylor Segraves| title = Clinical Manual of Sexual Disorders | publisher =[[American Psychiatric Pub]]|page=281|year = 2009|access-date=December 6, 2014| isbn = 978-1-58562-905-3 |url =https://books.google.com/books?id=YuP3Hb0TMLQC&pg=PA281}}</ref>

Sexual intercourse remains possible after major medical treatment of the reproductive organs and structures. This is especially true for women. Even after extensive gynecological surgical procedures (such as [[hysterectomy]], [[oophorectomy]], [[salpingectomy]], [[dilation and curettage]], [[hymenotomy]], [[Bartholin gland]] surgery, abscess removal, [[vestibulectomy]], [[labia minora]] reduction, [[cervical conization]], [[surgical]] and radiological cancer treatments and chemotherapy), coitus can continue. Reconstructive surgery remains an option for women who have experienced benign and malignant conditions.<ref name="Hoffman2012">{{cite book | last = Hoffman | first = Barbara | title = Williams gynecology | edition = 2nd | publisher = McGraw-Hill Medical |page=65 |location = New York | year = 2012 | isbn = 978-0-07-171672-7 }}</ref><!--pages 1020-1348-->

===Disabilities and other complications===
{{main| Sexuality and disability}}

Obstacles that those with [[disabilities]] face with regard to engaging in sexual intercourse include pain, [[Depression (mood)|depression]], fatigue, [[negative body image]], stiffness, functional impairment, anxiety, reduced [[libido]], hormonal imbalance, and drug treatment or side effects. Sexual functioning has been regularly identified as a neglected area of the quality of life in patients with [[rheumatoid arthritis]].<ref name="Tristano2014">{{cite journal|last1=Tristano|first1=Antonio G|title=Impact of rheumatoid arthritis on sexual function|journal=World Journal of Orthopedics|volume=5|issue=2|pages=107–11|year=2014|issn=2218-5836|doi=10.5312/wjo.v5.i2.107|pmid=24829873|pmc=4017303 |doi-access=free }}</ref> For those that must take opioids for pain control, sexual intercourse can become more difficult.<ref name="DeyoVon Korff2015">{{cite journal|last1=Deyo|first1=R. A.|last2=Von Korff|first2=M.|last3=Duhrkoop|first3=D.|title=Opioids for low back pain|journal=BMJ|volume=350|issue= |year=2015|pages=g6380|issn=1756-1833|doi=10.1136/bmj.g6380|pmid=25561513|pmc=6882374}}</ref> Having a [[stroke]] can also largely impact on the ability to engage in sexual intercourse.<ref name="HersonPalmateer2012">{{cite journal|last1=Herson|first1=Paco S.|last2=Palmateer|first2=Julie|last3=Hurn|first3=Patricia D.|title=Biological Sex and Mechanisms of Ischemic Brain Injury|journal=Translational Stroke Research|volume=4|issue=4|year=2012|pages=413–419|issn=1868-4483|doi=10.1007/s12975-012-0238-x|pmc=3733393|pmid=23930140}}</ref> Although disability-related pain, including as a result of [[cancer]], and mobility impairment can hamper sexual intercourse, in many cases, the most significant impediments to sexual intercourse for individuals with a disability are psychological.<ref name="Falvo">{{cite book |author=Donna Falvo| title = Medical and Psychosocial Aspects of Chronic Illness and Disability | publisher =[[Jones & Bartlett Publishers]]|page=367|year = 2013|access-date=December 7, 2014| isbn = 978-1-4496-9442-5 |url =https://books.google.com/books?id=SdM6FsykfWAC&pg=PA367}}</ref> In particular, people who have a disability can find sexual intercourse daunting due to issues involving their [[self-concept]] as a sexual being, or a partner's discomfort or perceived discomfort.<ref name="Falvo"/> Temporary difficulties can arise with [[alcohol and sex]], as alcohol can initially increase interest through disinhibition but decrease capacity with greater intake; however, disinhibition can vary depending on the culture.<ref name="WHO Risks">{{cite book|title=Alcohol Use and Sexual Risk Behaviour: A Cross-cultural Study in Eight Countries|publisher=[[World Health Organization]]|year=2005|pages=135 pages|access-date = March 30, 2013 |isbn = 978-92-4-156289-8| url =https://books.google.com/books?id=fZ1eBPIIr48C }}</ref><ref name="Aggleton">{{cite book |author=Peter Aggleton |author2=Andrew Ball |author3=Purnima Mane |author3-link=Purnima Mane | title = Sex, Drugs and Young People: International Perspectives | publisher =[[Routledge]]|pages=130–133|year = 2013|access-date=December 7, 2014| isbn = 978-1-134-33309-7 |url = https://books.google.com/books?id=dWknAAAAQBAJ&pg=PA130}}</ref>

People with [[mental disabilities]] also are subject to challenges in participating in sexual intercourse. This can include the lack of a knowledgeable healthcare provider trained and experienced in counseling those with [[intellectual disabilities]] on sexual intercourse. Those with intellectual disabilities may have hesitations regarding the discussion of the topic of sex, a lack of sexual knowledge and limited opportunities for sex education.<ref>{{cite journal |last1=Medina-Rico |first1=Mauricio |last2=López-Ramos |first2=Hugo |last3=Quiñonez |first3=Andrés |title=Sexuality in People with Intellectual Disability: Review of Literature |journal=Sexuality and Disability |date=September 1, 2018 |volume=36 |issue=3 |pages=231–248 |doi=10.1007/s11195-017-9508-6 |s2cid=255009541 |url=https://link.springer.com/article/10.1007/s11195-017-9508-6 |language=en |issn=1573-6717}}</ref> In addition there are other barriers such as a higher prevalence of sexual abuse and assault. These crimes often remain underreported. There remains a lack of "dialogue around this population's human right to consensual sexual expression, undertreatment of menstrual disorders, and legal and systemic barriers". Women with intellectual disability may lack sexual health care and sex education. They may not recognize sexual abuse. Consensual sexual intercourse is not always an option for some. Those with intellectual disability may have limited knowledge and access to contraception, screening for sexually transmitted infections and cervical cancer.<ref name="GreenwoodWilkinson2013">{{cite journal|last1=Greenwood|first1=Nechama W.|last2=Wilkinson|first2=Joanne|title=Sexual and Reproductive Health Care for Women with Intellectual Disabilities: A Primary Care Perspective|journal=International Journal of Family Medicine|volume=2013|year=2013|pages=1–8|issn=2090-2042|doi=10.1155/2013/642472|pmid=24455249|pmc=3876698|doi-access=free}}</ref>

==Social effects==
{{See also|Human mating strategies|Pair bond}}

===Adults===
Sexual intercourse may be for reproductive, relational, or recreational purposes.<ref name="Harvey J">{{cite book| first1=John H. |last1=Harvey |first2=Amy |last2=Wenzel |first3=Susan |last3=Sprecher|title =The Handbook of Sexuality in Close Relationships|publisher = [[Psychology Press]] | year = 2004 | pages = 172–173|isbn =1-135-62470-4|url=https://books.google.com/books?id=qsl4AgAAQBAJ}}</ref> It often plays a strong role in [[human bonding]].<ref name="Freberg"/> In many societies, it is normal for couples to have sexual intercourse while using some method of birth control, sharing pleasure and strengthening their emotional bond through sexual activity even though they are deliberately avoiding pregnancy.<ref name="Freberg"/>

In humans and [[bonobo]]s, the female undergoes relatively [[concealed ovulation]] so that male and female partners commonly do not know whether she is fertile at any given moment. One possible reason for this distinct biological feature may be formation of strong emotional bonds between sexual partners important for social interactions and, in the case of humans, long-term partnership rather than immediate sexual reproduction.<ref name="Reis">{{Cite book|author= Harry T. Reis|author2= Susan Sprecher |author-link=Harry Reis | title = Encyclopedia of Human Relationships |volume=1| year = 2009 | publisher = [[SAGE Publications|SAGE]] |pages=541–543 | isbn = 978-1-4129-5846-2| url=https://books.google.com/books?id=3EkOwvSAtL4C&pg=PA541}}</ref>

[[Sexual dissatisfaction]] due to the lack of sexual intercourse is associated with increased risk of [[divorce]] and relationship dissolution, especially for men.<ref name="Munck">{{cite book| author = Victor C. De Munck|title =Romantic Love and Sexual Behavior: Perspectives from the Social Sciences|publisher = [[Greenwood Publishing Group]] | year = 1998 | pages = 148–149 | access-date = December 9, 2014 |isbn = 978-0-275-95726-1| url =https://books.google.com/books?id=I78VnFoINgQC&pg=PA148}}</ref><ref name="Howe">{{cite book| author = Tasha R. Howe|title =Marriages and Families in the 21st Century: A Bioecological Approach|publisher = [[John Wiley & Sons]] | year = 2011 | page = 411 | access-date = December 9, 2014 |isbn = 978-1-4051-9501-0| url =https://books.google.com/books?id=UHaLL0pYwhMC&pg=PA411}}</ref><ref name="Fine">{{cite book|author1=Mark A Fine |author2=John H. Harvey |title =Handbook of Divorce and Relationship Dissolution|publisher = [[Psychology Press]] | year = 2013 | page = 160 | access-date = December 9, 2014 |isbn = 978-1-317-82421-3| url =https://books.google.com/books?id=wGZlAgAAQBAJ&pg=PA160}}</ref> Some research, however, indicates that general dissatisfaction with [[marriage]] for men results if their wives [[flirted]] with, erotically kissed or became romantically or sexually involved with another man ([[infidelity]]),<ref name="Munck"/><ref name="Howe"/> and that this is especially the case for men with a lower emotional and composite marital satisfaction.<ref name="Fine"/> Other studies report that the lack of sexual intercourse does not significantly result in divorce, though it is commonly one of the various contributors to it.<ref name="Reinisch2">{{cite book| author = June M. Reinisch| author2 = Ruth Beasley| author-link = June Reinisch | title = The Kinsey Institute New Report On Sex| publisher = [[Macmillan Publishers|Macmillan]] | year = 1991 | page = 74| access-date = December 9, 2014 |isbn = 978-0-312-06386-3| url =https://books.google.com/books?id=KsW6wPiXEd0C&pg=PA74}}</ref><ref name="Schwartz2">{{cite book| author = Pepper Schwartz| author2 = Virginia Rutter| author-link=Pepper Schwartz | author2-link=Virginia Rutter |title =The Gender of Sexuality|publisher = [[Rowman & Littlefield]] | year = 1998 | page = 129 | access-date = December 9, 2014 |isbn = 978-0-8039-9042-5| url =https://books.google.com/books?id=7bWlvcpYGUcC&pg=PA129}}</ref> According to the 2010 National Survey of Sexual Health and Behavior (NSSHB), men whose most recent sexual encounter was with a relationship partner reported greater arousal, greater pleasure, fewer problems with erectile function, orgasm, and less pain during the event than men whose last sexual encounter was with a non-relationship partner.<ref name="Yarber">{{cite book| author = William Yarber| author2 = Barbara Sayad| author3 = Bryan Strong| author3-link = Bryan Strong|title =Human Sexuality: Diversity in Contemporary America|edition =Eighth|publisher = [[McGraw-Hill Higher Education]] | year = 2012 | page = 445 | access-date = December 9, 2014 |isbn = 978-0-07-743525-7| url =https://books.google.com/books?id=EWz7twAACAAJ&q=Human+Sexuality:+Diversity+in+Contemporary+America}}</ref>

For women, there is often a complaint about the lack of their spouses' sexual spontaneity. Decreased sexual activity among these women may be the result of their perceived failure to maintain ideal [[physical attractiveness]] or because their sexual partners' health issues have hindered sexual intercourse.<ref name="Montemurro">{{cite book| author = Beth Montemurro|title =Deserving Desire: Women's Stories of Sexual Evolution|publisher = [[Rutgers University Press]] | year = 2014 | page = 169 | access-date = December 9, 2014 |isbn = 978-0-8135-7306-9| url =https://books.google.com/books?id=1XVYBQAAQBAJ&pg=PT169}}</ref> Some women express that their most satisfying sexual experiences entail being connected to someone, rather than solely basing satisfaction on orgasm.<ref name="Wincze"/><ref name="Gurian">{{cite book| author = Michael Gurian| author-link=Michael Gurian|title =The Wonder of Aging: A New Approach to Embracing Life After Fifty|publisher = [[Simon & Schuster]] | year = 2013 | page = 178 | access-date = December 9, 2014 |isbn = 978-1-4767-0671-9| url =https://books.google.com/books?id=XyS5ebuXJWgC&pg=PT178}}</ref> With regard to divorce, women are more likely to divorce their spouses for a [[one-night stand]] or various infidelities if they are in less cooperative or high-conflict marriages.<ref name="Fine"/>

Research additionally indicates that non-married couples who are [[cohabiting]] engage in sexual intercourse more often than married couples, and are more likely to participate in sexual activity outside of their sexual relationships; this may be due to the "[[honeymoon]]" effect (the newness or novelty of sexual intercourse with the partner), since sexual intercourse is usually practiced less the longer a couple is married, with couples engaging in sexual intercourse or other sexual activity once or twice a week, or approximately six to seven times a month.<ref name="Strong2">{{cite book| author = Bryan Strong| author2 = Theodore Cohen |author-link=Bryan Strong|title =The Marriage and Family Experience: Intimate Relationships in a Changing Society|publisher = [[Cengage Learning]] | year = 2013 | page = 212 | access-date = December 9, 2014 |isbn =978-1-285-53189-2| url =https://books.google.com/books?id=6ZIWAAAAQBAJ&pg=PT237}}</ref> [[Sexuality in older age]] also affects the frequency of sexual intercourse, as older people generally engage in sexual intercourse less frequently than younger people do.<ref name="Strong2"/>

===Adolescents===
{{Main|Adolescent sexuality}}
Adolescents commonly use sexual intercourse for relational and recreational purposes, which may negatively or positively impact their lives. For example, while [[teenage pregnancy]] may be welcomed in some cultures, it is also commonly disparaged, and research suggests that the [[Precocious puberty|earlier onset of puberty]] for children puts pressure on children and teenagers to act like adults before they are emotionally or cognitively ready.<ref name="sex lives3">{{cite book| title=The Sex Lives of Teenagers| isbn=978-0-452-28260-5| last=Ponton| first=Lynn| author-link=Lynn Ponton| year=2000| page=[https://archive.org/details/sexlivesofteenag00lynn/page/3 3]| publisher=[[Dutton Publishing]]| url=https://archive.org/details/sexlivesofteenag00lynn/page/3}}</ref> Some studies have concluded that engaging in sexual intercourse leaves adolescents, especially girls, with higher levels of stress and depression, and that girls may be likelier to engage in sexual risk (such as sexual intercourse without the use of a condom),<ref name="DiClemente">{{cite book| author = Ralph J. DiClemente| author2 = John S. Santelli| author3 = Richard A. Crosby|title = Adolescent Health: Understanding and Preventing Risk Behaviors| publisher = [[John Wiley & Sons]] | year = 2009 | pages = 521–522| access-date = December 7, 2014 |isbn = 978-0-470-45279-0| url =https://books.google.com/books?id=KcrwY8eCwcQC&pg=PT521}}</ref><ref name="Abaied">{{cite book| author = Jamie L Abaied| author2 = Deepika Anand| author3 = Tracey L Auster| author4 = Daniel BE|title =The Oxford Handbook of Depression and Comorbidity| publisher = [[Oxford University Press]] | year = 2014 | page = 450 | access-date = December 7, 2014 |isbn = 978-0-19-979700-4| url =https://books.google.com/books?id=hzpsAwAAQBAJ&pg=PA450}}</ref> but it may be that further research is needed in these areas.<ref name="Abaied"/> In some countries, such as the United States, [[sex education]] and [[abstinence-only sex education]] curricula are available to educate adolescents about sexual activity; these programs are controversial, as debate exists as to whether teaching children and adolescents about sexual intercourse or other sexual activity should only be left up to parents or other [[caregiver]]s.<ref name="Ryan">{{cite book| author =Kevin Ryan| author2 =James Cooper|title =Those Who Can, Teach|publisher = [[Cengage Learning]] | year = 2008 | page = 110 | access-date = December 9, 2014 |isbn = 978-0-547-20488-8| url =https://books.google.com/books?id=rqmdR6Xrgq8C&pg=PA110}}</ref>

Some studies from the 1970s through 1990s suggested an association between [[self-esteem]] and sexual intercourse among adolescents,<ref name="Lerner 2">{{cite book| first1 = Richard M. | last1 = Lerner | first2 = Daniel F. | last2 = Perkins | name-list-style = vanc |title = Social Interactions in Adolescence and Promoting Positive Social Contributions of Youth| publisher = [[Taylor & Francis]] | year = 1999 | page = 124| access-date = April 14, 2017 |isbn = 978-0-8153-3295-4| url =https://books.google.com/books?id=BunEIQylaJAC&pg=PA124}}</ref> while other studies, from the 1980s and 1990s, reported that the research generally indicates little or no relationship between self-esteem and sexual activity among adolescents.<ref name="Kowalski">{{cite book |vauthors=Kowalski RM, Leary MR |title =The Interface of Social and Clinical Psychology: Key Readings| publisher = [[Psychology Press]] | year = 2004 | page = 121| access-date = April 14, 2017 |isbn = 978-1-84169-087-2| url =https://books.google.com/books?id=qkEdaQ4heGgC&pg=PA121}}</ref> By the 1990s, the evidence mostly supported the latter,<ref name="Kowalski"/> and further research has supported little or no relationship between self-esteem and sexual activity among adolescents.<ref name="Guindon">{{cite book| author =Mary H. Guindon|title =Self-Esteem Across the Lifespan: Issues and Interventions| publisher = [[Taylor & Francis]] | year = 2009 | page = 147| access-date = April 14, 2017 |isbn = 978-1-84169-087-2| url =https://books.google.com/books?id=EcoPo06GYCMC&pg=PA147}}</ref><ref name="Lisa Arai">{{cite book| author =Lisa Arai|title =Teenage Pregnancy: The Making and Unmaking of a Problem| publisher = [[Policy Press]] | year = 2009 | page = 147| access-date = April 14, 2017 |isbn = 978-1-84742-074-9| url =https://books.google.com/books?id=qzOguz7GqNoC&pg=PA32}}</ref> Scholar Lisa Arai stated, "The idea that early sexual activity and pregnancy is linked to low self-esteem became fashionable in the latter half of the 20th century, particularly in the US," adding that, "Yet, in a systematic review of the relationship between self-esteem and teenagers' sexual behaviours, attitudes and intentions (which analyzed findings from 38 publications) 62% of behavioral findings and 72% of the attitudinal findings exhibited no statistically significant associations (Goodson et al, 2006)."<ref name="Lisa Arai"/> Studies that do find a link suggest that non-virgin boys have higher self-esteem than virgin boys and that girls who have low self-esteem and poor [[self-image]] are more prone to risk-taking behaviors, such as unprotected sex and [[multiple sexual partners]].<ref name="Lerner 2"/><ref name="Guindon"/><ref name="Lisa Arai"/>

Psychiatrist [[Lynn Ponton]] wrote, "All adolescents have sex lives, whether they are sexually active with others, with themselves, or seemingly not at all", and that viewing adolescent sexuality as a potentially positive experience, rather than as something inherently dangerous, may help young people develop healthier patterns and make more positive choices regarding sexual activity.<ref name="sex lives3" /> Researchers state that long-term romantic relationships allow adolescents to gain the skills necessary for high-quality relationships later in life.<ref>Madsen S., Collins W. A. (2005). Differential predictions of young adult romantic relationships from transitory vs. longer romantic experiences during adolescence. Presented at ''Biennial Meeting of the Society for Research on Child Development'', Atlanta, Georgia.</ref> Overall, positive romantic relationships among adolescents can result in long-term benefits. High-quality romantic relationships are associated with higher commitment in early adulthood,<ref>{{ill|Seiffge-Krenke I.|de|Inge Seiffge-Krenke}}, Lang J. (2002). Forming and maintaining romantic relations from early adolescence to young adulthood: evidence of a developmental sequence. Presented at 19th ''Biennial Meeting of the Society for Research on Adolescence'', New Orleans, Louisiana.</ref> and are positively associated with social competence.<ref>{{cite journal |vauthors=Pearce MJ, Boergers J, Prinstein MJ | s2cid = 154577 | title = Adolescent obesity, overt and relational peer victimization, and romantic relationships | journal = Obesity Research | volume = 10 | issue = 5 | pages = 386–93 | year = 2002 | pmid = 12006638 | doi = 10.1038/oby.2002.53 | doi-access =  }}</ref><ref>{{cite journal |vauthors=Zimmer-Gembeck MJ, Siebenbruner J, Collins WA | title = A prospective study of intraindividual and peer influences on adolescents' heterosexual romantic and sexual behavior | journal = Archives of Sexual Behavior | volume = 33 | issue = 4 | pages = 381–394 | year = 2004 | pmid = 15162084 | doi = 10.1023/B:ASEB.0000028891.16654.2c | s2cid = 1054833 }}</ref>

==Ethical, religious, and legal views==
===General===
{{See also|Sexual ethics|Religion and sexuality|Sex and the law}}
[[File:Erotic scenes Louvre G13 n4.jpg|thumb|Erotic painting on ancient Greek [[kylix]]]]
While sexual intercourse, as coitus, is the natural mode of reproduction for the human species, humans have intricate moral and ethical guidelines which regulate the practice of sexual intercourse and vary according to [[religion and sexuality|religious]] and governmental laws. Some governments and religions also have strict designations of what they consider appropriate and inappropriate sexual behavior, which include restrictions on the types of sex acts which are permissible. A historically prohibited or regulated sex act is anal sex.<ref>[[William N. Eskridge Jr.]] Dishonorable Passions: Sodomy Laws in America, 1861–2003. (2008) Viking Adult. {{ISBN|0-670-01862-7}}</ref><ref>Noelle N. R. Quenivet. Sexual Offenses in Armed Conflict & International Law. (2005) Hotei Publishing. {{ISBN|1-57105-341-7}}</ref>

===Sexual offenses===
Sexual intercourse with a person against their will, or without their [[Consent#Sexual activity|consent]], is [[rape]], but may also be called ''[[sexual assault]]''; it is considered a serious [[criminal law|crime]] in most countries.<ref name="Sex and Society">{{cite book|author=Marshall Cavendish Corporation | title = Sex and Society | publisher = [[Marshall Cavendish Corporation]] | year = 2010 | pages = 143–144 | access-date = August 25, 2013|isbn = 978-0-7614-7906-2|url =https://books.google.com/books?id=aVDZchwkIMEC&pg=PA143}}</ref><ref name="Greenberg2">{{cite book|author=Jerrold S. Greenberg|author2=Clint E. Bruess|author3=Sarah C. Conklin| title = Exploring the Dimensions of Human Sexuality| publisher = [[Jones & Bartlett Learning]] | year = 2010 | page = 515 | access-date = August 25, 2013|isbn = 978-0-7637-7660-2|url =https://books.google.com/books?id=1NC5R0RozBYC&pg=PA515}}</ref> More than 90% of rape victims are female, 99% of rapists male, and only about 5% of rapists are strangers to the victims.<ref name="Greenberg2"/>

Most countries have [[age of consent]] laws which set the minimum legal age with whom an older person may engage in sexual intercourse, usually set at 16 to 18, but ranges from 12 to 20, years of age. In some societies, an age of consent is set by non-statutory custom or tradition.<ref name="Kinnear">{{cite book|author=Karen L. Kinnear| title = Childhood Sexual Abuse: A Reference Handbook| publisher = [[ABC-CLIO]] | year = 2007 | page = 89 | access-date = August 25, 2013|isbn = 978-1-85109-905-4|url =https://books.google.com/books?id=V1rogCrcOMwC}}</ref> Sex with a person under the age of consent, regardless of their stated consent, is often considered sexual assault or [[statutory rape]] depending on differences in ages of the participants. Some countries treat any sex with a person of diminished or insufficient mental capacity to give consent, regardless of age, as rape.<ref>{{cite journal |last=Reed|first=E. J.|title=Criminal Law and the Capacity of Mentally Retarded Persons to Consent to Sexual Activity |journal=[[Virginia Law Review]] |year=1997|volume=83|issue=4 |pages=799–827|jstor=1073749|doi=10.2307/1073749}}</ref>
[[File:Slevogt Faun and a Girl.jpg|thumb|left|[[Max Slevogt]] depiction of rape]]
Robert Francoeur et al. stated that "prior to the 1970s, rape definitions of sex often included only penile-vaginal sexual intercourse."<ref name="Francoeur">{{cite book | title = The Continuum Complete International Encyclopedia of Sexuality | publisher = [[Continuum International Publishing Group]] | year = 2004 | page = 173 | access-date = April 30, 2013|isbn = 978-0-8264-1488-5| url =https://books.google.com/books?id=PQMTzc6y8ZAC&pg=PA173 | first1 = Robert T. | last1 = Francoeur | author1-link = Robert T. Francoeur | first2 = Raymond J. | last2 = Noonan | first3 = Beldina | last3 = Opiyo-Omolo | name-list-style = vanc }}</ref> Authors Pamela J. Kalbfleisch and Michael J. Cody stated that this made it so that if "sex means penile-vaginal intercourse, then rape means forced penile-vaginal intercourse, and other sexual behaviors&nbsp;– such as fondling a person's genitals without her or his consent, forced oral sex, and same-sex coercion&nbsp;– are not considered rape"; they stated that "although some other forms of forced sexual contact are included within the legal category of sodomy (e.g., anal penetration and oral-genital contact), many unwanted sexual contacts have no legal grounding as rape in some states".<ref name="Kalbfleisch"/> Ken Plumber argued that the legal meaning "of rape in most countries is unlawful sexual intercourse which means the penis must penetrate the vagina" and that "other forms of sexual violence towards women such as forced oral sex or anal intercourse, or the insertion of other objects into the vagina, constitute the 'less serious' crime of sexual assault".<ref name="Plummer">{{cite book| author = Ken Plummer | author-link = Ken Plummer (sociologist) | title = Modern Homosexualities: Fragments of Lesbian and Gay Experiences | publisher = [[Routledge]] | year = 2002 | pages = 187–191 | access-date = August 24, 2013|isbn =978-1-134-92242-0 | url=https://books.google.com/books?id=OSO3q4XEfz4C&pg=PA189|quote=[S]ome sexual practices are regarded as inherently better (normal, natural, more satisfying) than others, with vaginal intercourse privileged as the 'Real Thing.' Such beliefs, influenced by views about sex as ultimately a reproductive function, continue to be perpetuated through discourses on sex despite a number of important contradictions.}}</ref>

Over time, the meaning of rape broadened in some parts of the world to include many types of sexual penetration, including anal intercourse, fellatio, cunnilingus, and penetration of the genitals or rectum by an inanimate object.<ref name="Francoeur"/> Until 2012, the [[Federal Bureau of Investigation]] (FBI) still considered rape a crime solely committed by men against women. In 2012, they changed the meaning from "The carnal knowledge of a female forcibly and against her will" to "The penetration, no matter how slight, of the vagina or anus with any body part or object, or oral penetration by a sex organ of another person, without the consent of the victim." The meaning does not change federal or state criminal codes or impact charging and prosecution on the federal, state or local level, but instead assures that rape will be more accurately reported nationwide.<ref>{{cite web |url=http://blogs.usdoj.gov/blog/archives/1801 |title=An Updated Definition of Rape (U.S. Dept of Justice, January 6, 2012) |access-date=October 30, 2014 |archive-url=https://web.archive.org/web/20120313021145/http://blogs.usdoj.gov/blog/archives/1801 |archive-date=March 13, 2012 |url-status=dead}}</ref><ref>{{cite news |url=https://www.nytimes.com/2012/01/07/us/politics/federal-crime-statistics-to-expand-rape-definition.html |title=U.S. to Expand Rape Definition in Crime Statistics|newspaper=The New York Times|date=January 6, 2012 |last1=Savage|first1=Charlie|author1-link=Charlie Savage (author)}}</ref> In some instances, penetration is not required for the act to be categorized as rape.<ref name="Book04">{{cite book |editor-last=Smith |editor-first=Merril D. |title=Encyclopedia of rape |year=2004 |publisher=Greenwood Press |location=Westport, Conn. |isbn=978-0-313-32687-5 |pages=169–170 |edition=1st}}</ref>

In most societies around the world, the concept of [[incest]] exists and is criminalized. James Roffee, a senior lecturer in criminology at [[Monash University]],<ref>{{cite web |url=http://monash.edu/research/explore/en/persons/james-roffee(896c15d7-6f28-4bf0-8a0f-b7d6ff1553e0).html |title=Dr James Roffee|publisher=Monash university|access-date=May 22, 2017|archive-url=https://web.archive.org/web/20170204003059/http://monash.edu/research/explore/en/persons/james-roffee%28896c15d7-6f28-4bf0-8a0f-b7d6ff1553e0%29.html|archive-date=February 4, 2017|url-status=dead}}</ref> addressed potential harm associated with familial sexual activity, such as resulting children born with deficiencies. However, the law is more concerned with protecting the rights of people who are potentially subjected to such abuse. This is why familial sexual relationships are criminalized, even if all parties are consensual. There are laws prohibiting all kinds of sexual activity between relatives, not necessarily penetrative sex. These laws refer to grandparents, parents, children, siblings, aunts and uncles. There are differences between states in terms of the severity of punishments and what they consider to be a relative, including biological parents, step-parents, adoptive parents and half-siblings.<ref>{{cite journal |doi=10.1093/hrlr/ngu023 |last=Roffee |first=J. A. |date=September 2014 |title=No Consensus on Incest? Criminalisation and Compatibility with the European Convention on Human Rights |journal=Human Rights Law Review |volume=14 |issue=3 |pages=541–572}}</ref>

Another sexual matter concerning consent is [[zoophilia]], which is a [[paraphilia]] involving sexual activity between human and non-human animals, or a fixation on such practice.<ref name="DSM">{{cite book |title=Diagnostic and Statistical Manual of Mental Disorders: DSM-IV | publisher = [[American Psychiatric Association]] |location=Washington, DC |year=2000 |isbn=978-0-89042-025-6 | title-link = Diagnostic and Statistical Manual of Mental Disorders }}</ref><ref name="Milner2008">{{cite book |veditors = Laws DR, O'Donohue WT |name-list-style = amp | last = Milner | first = JS |author2=Dopke CA | title = Sexual Deviance, Second Edition: Theory, Assessment, and Treatment | publisher = [[The Guilford Press]] | location = New York | year = 2008 | pages = [https://books.google.com/books?id=yIXG9FuqbaIC&pg=PA385 384–418] |isbn=978-1-59385-605-2 | chapter = Paraphilia Not Otherwise Specified: Psychopathology and theory}}</ref><ref name="Seto2000">{{cite book |editor = Hersen M |editor2 = Van Hasselt VB | title = Aggression and violence: an introductory text |publisher= [[Allyn & Bacon]] |location=Boston |year=2000 |pages= 198–213 |isbn=978-0-205-26721-7 | last = Seto| first = MC|author2=Barbaree HE | chapter = Paraphilias}}</ref> Human sexual activity with non-human animals is not outlawed in some jurisdictions, but it is illegal in others under [[animal abuse]] laws or laws dealing with [[crimes against nature]].<ref name="Perdue">{{cite book| author =Abigail Perdue| author2 =Randall Lockwood|title=Animal Cruelty and Freedom of Speech: When Worlds Collide|publisher =[[Purdue University Press]]| year = 2014 | pages = 6–8| access-date = December 9, 2014 |isbn = 978-1-55753-633-4| url =https://books.google.com/books?id=R1ncAwAAQBAJ&pg=PA6}}</ref>

===Romantic relationships===
[[File:Lawrence Alma-Tadema Courtship - The Proposal.jpg|thumb|right|[[Lawrence Alma-Tadema]] depiction of [[courtship]] and a [[marriage proposal]]]]

====Marriage and relationships====
Sexual intercourse has traditionally been considered an essential part of a marriage, with many religious customs requiring [[consummation]] of the marriage and citing marriage as the most appropriate union for sexual reproduction (procreation).<!-- NOTE: This is also sourced in the bullet-point examples list below.--><ref name="Hogan">{{cite book| author =Margaret Monahan Hogan|title =Marriage as a Relationship: Real and Rational|publisher = [[Marquette University Press]] | year = 2002 | page = 88 | access-date = September 1, 2015 |isbn = 978-0-87462-657-5| url =https://books.google.com/books?id=HuztAAAAMAAJ&q=Marriage+as+a+Relationship:+Real+and+Rational}}</ref> In such cases, a failure for any reason to consummate the marriage would be considered a ground for [[annulment]] (which does not require a divorce process). Sexual relations between marriage partners have been a "marital right" in various societies and religions, both historically and in modern times, especially with regard to a husband's rights to his wife.<ref name="Dwyer">{{cite book| author =James G. Dwyer|title =Religious Schools V. Children's Rights|publisher = [[Cornell University Press]] | year = 2001 | pages = 72–73 | access-date = August 31, 2015 |isbn = 978-0-8014-8731-6| url =https://books.google.com/books?id=QDwD4huqyysC&pg=PA72}}</ref><ref name="Green">{{cite book| author =Ronald Green|author-link=Ronald Michael Green|title =Religion and Sexual Health: Ethical, Theological, and Clinical Perspectives, Volume 1 of Theology and Medicine|publisher = [[Springer Science & Business Media]] | year = 2013 | page = 112 | access-date = August 31, 2015 |isbn = 978-94-015-7963-6| url =https://books.google.com/books?id=h2mvBQAAQBAJ&pg=PT112}}</ref><ref name="Brook">{{cite book| author =Heather Brook|title = Conjugality: Marriage and Marriage-like Relationships Before the Law|publisher = [[Palgrave Macmillan]] | year = 2015 | pages = 71–73 | access-date = August 31, 2015 |isbn = 978-1-137-48091-0| url =https://books.google.com/books?id=rP2_CQAAQBAJ&pg=PA71}}</ref> Until the late 20th century, there was usually a [[marital rape|marital exemption]] in [[rape law]]s which precluded a husband from being prosecuted under the rape law for forced sex with his wife.<ref name="Steinmetz">{{cite book| author =Suzanne K. Steinmetz| author2 =Marvin B. Sussman|title = Handbook of Marriage and the Family|publisher = [[Springer Science & Business Media]] | year = 2013 | pages = 787–788 | access-date = August 31, 2014 |isbn = 978-1-4615-7151-3| url =https://books.google.com/books?id=T6XwBwAAQBAJ&pg=PA787}}</ref> Author Oshisanya, 'lai Oshitokunbo stated, "As the legal status of women has changed, the concept of a married man's or woman's marital right to sexual intercourse has become less widely held."<ref name="Oshitokunbo">{{cite book| author =Oshisanya, 'lai Oshitokunbo|title = An Almanac of Contemporary Judicial Restatements (Criminal & Quasi Criminal Law & Procedure) vol. iii: Almanac vol. iii|publisher = Almanac Foundation | year = 2015 | page = 132 | access-date = August 31, 2015 |isbn = 978-978-51200-3-5| url =https://books.google.com/books?id=fsDOBAAAQBAJ&pg=PA132}}</ref>

[[Adultery]] (engaging in sexual intercourse with someone other than one's spouse) has been, and remains, a criminal offense in some jurisdictions.<ref name="Brundage">{{cite book| author =[[James A. Brundage]]|title =Law, Sex, and Christian Society in Medieval Europe|publisher = [[University of Chicago Press]] | year = 2009 | pages = 609–611 | access-date = August 31, 2015 |isbn = 978-0-226-07789-5| url =https://books.google.com/books?id=SiGe-Zf0nTIC&pg=PA609}}</ref><ref name="Carlan">{{cite book| author =Philip Carlan| author2 =Lisa S. Nored| author3 =Ragan A. Downey|title =An Introduction to Criminal Law|publisher = [[Jones & Bartlett Publishers]] | year = 2011 | page = 139 | access-date = August 31, 2015 |isbn = 978-1-4496-4721-6| url =https://books.google.com/books?id=8-tPwZyNWzkC&pg=PA139}}</ref> Sexual intercourse between unmarried partners and cohabitation of an unmarried couple are also illegal in some jurisdictions.<ref name="BBC News">{{cite news|title = Can Iran 'control' its cohabiting couples?|date = December 10, 2014|access-date=August 31, 2015|work = BBC News |url=https://www.bbc.com/news/world-middle-east-30391593}}</ref><ref name="amnesty.org">{{cite web|title=Amnesty International Report 2014/15|date=2014|access-date=August 31, 2015|publisher=[[amnesty.org]]|url=https://www.amnesty.org/en/countries/middle-east-and-north-africa/morocco/report-morocco/|archive-date=May 4, 2017|archive-url=https://web.archive.org/web/20170504233053/https://www.amnesty.org/en/countries/middle-east-and-north-africa/morocco/report-morocco/|url-status=dead}}</ref> Conversely, in other countries, marriage is not required, socially or legally, in order to have sexual intercourse or to procreate (for example, the majority of births are outside of marriage in countries such as Iceland, Norway, Sweden, Denmark, Bulgaria, Estonia, Slovenia, France, Belgium).<ref name="europa.eu">{{cite web|title =Share of live births outside marriage|date = March 2, 2015|access-date=August 31, 2015|publisher = [[europa.eu]] |url=http://ec.europa.eu/eurostat/tgm/table.do?tab=table&plugin=1&language=en&pcode=tps00018}}</ref>

With regard to [[divorce law]]s, the refusal to engage in sexual intercourse with one's spouse may give rise to a [[grounds for divorce]], which may be listed under "grounds of abandonment".<ref name=Choudhri>{{cite book| author =Choudhri, Nihara K|title =The complete guide to divorce law|publisher = [[Citadel Press]] | year = 2004 | pages = 8–9 | access-date = August 30, 2015 |isbn = 978-0-8065-2528-0| url =https://books.google.com/books?id=5cLIO2yUA4gC&pg=PA8}}</ref> Concerning [[no-fault divorce]] jurisdictions, author James G. Dwyer stated that no-fault divorce laws "have made it much easier for a woman to exit a marital relationship, and wives have obtained greater control over their bodies while in a marriage" because of legislative and judicial changes regarding the concept of a marital exemption when a man rapes his wife.<ref name="Dwyer"/>

There are various legal positions regarding the meaning and legality of sexual intercourse between persons of the same sex or gender. For example, in the 2003 [[New Hampshire Supreme Court]] case [[Blanchflower v. Blanchflower]], it was held that female same-sex sexual relations, and same-sex sexual practices in general, did not constitute sexual intercourse, based on a 1961 entry in ''[[Webster's Third New International Dictionary]]'' that categorizes sexual intercourse as coitus; and thereby an accused wife in a divorce case was found not guilty of [[adultery]].<ref name="GLAD, B vs. B">{{cite web|title=Blanchflower v. Blanchflower and Mayer|publisher=[[Gay & Lesbian Advocates & Defenders]] (GLAD)|date=December 31, 2003|access-date=August 9, 2013|url=http://www.glad.org/work/cases/blanchflower-v-blanchflower-and-mayer|archive-date=November 21, 2016|archive-url=https://web.archive.org/web/20161121174107/http://www.glad.org/work/cases/blanchflower-v-blanchflower-and-mayer|url-status=dead}}</ref><ref name="courts.state.nh.us">{{cite web |title=In the Matter of David G. Blanchflower and Sian E. Blanchflower |website=New Hampshire Judicial Branch |date=November 7, 2003 |access-date=September 3, 2023 |url=http://www.courts.state.nh.us/supreme/opinions/2003/blanc150.htm |url-status=dead |archive-url=https://web.archive.org/web/20040212230629/http://www.courts.state.nh.us/supreme/opinions/2003/blanc150.htm |archive-date=February 12, 2004}}{{cbignore}}</ref> Some countries consider same-sex sexual behavior an offense punishable by imprisonment or execution; this is the case, for example, [[LGBT in Islam|in Islamic countries]], including [[LGBT rights in Iran|LGBT issues in Iran]].<ref>[[Janet Afary]]. Sexual Politics in Modern Iran. (2009) [[Cambridge University Press]]. {{ISBN|0-521-89846-3}}</ref><ref name="amnesty.org2">{{cite web|title=PUBLIC AI Index: MDE 13/010/2008. UA 17/08 Fear of imminent execution/ flogging|publisher=[[Amnesty International]]|access-date=December 22, 2013|url=http://www2.amnesty.se/uaonnet.nsf/dfab8d7f58eec102c1257011006466e1/fd0b99f84da0da71c12573d7003a87a5?OpenDocument&Click=|url-status=dead|archive-url=https://web.archive.org/web/20160305004923/http://www2.amnesty.se/uaonnet.nsf/dfab8d7f58eec102c1257011006466e1/fd0b99f84da0da71c12573d7003a87a5?OpenDocument&Click=|archive-date=March 5, 2016}}</ref>

Opposition to [[same-sex marriage]] is largely based on the belief that sexual intercourse and sexual orientation should be of a heterosexual nature.<ref name="Cahn and Carbone">{{Cite book|author1=Naomi R. Cahn |author2=June Carbone |title = Red families v. blue families: legal polarization and the creation of culture | publisher = [[Oxford University Press]] US| year = 2010 |page =129| isbn = 978-0-19-537217-5|access-date=July 29, 2011|url=https://books.google.com/books?id=F6eeGny49J4C&pg=PA129}}</ref><ref name="Cantor">{{Cite book| author =Donald J. Cantor|title =Same-sex marriage: the legal and psychological evolution in America| publisher = [[Wesleyan University Press]]| year = 2006 |pages =1–191| isbn = 978-0-8195-6812-0|access-date=July 29, 2011|url=https://books.google.com/books?id=lydHmmrHB8QC}}</ref><ref name="psychological">{{cite web|title=Resolution on Sexual Orientation and Marriage |author=[[American Psychological Association]] |year=2004| access-date=September 1, 2015 |url=http://www.apa.org/pi/families/resources/task-force/military-deployment.pdf}}</ref> The recognition of such marriages is a [[civil rights]], political, social, moral and religious issue in many nations, and the conflicts arise over whether same-sex couples should be allowed to enter into marriage, be required to use a different status (such as a [[civil union]], which either grant equal rights as marriage or limited rights in comparison to marriage), or not have any such rights. A related issue is whether the word ''marriage'' should be applied.<ref name="Cantor"/><ref name="psychological"/>

====Religious views====
{{See also|Religion and sexuality}}
There are wide differences in religious views with regard to sexual intercourse in or outside of marriage:
* Most denominations of [[Christianity]], including [[Catholicism]], have strict views or rules on what sexual practices are and are not acceptable.<ref name="Akin">{{Cite book|author=Daniel L. Akin|author-link=Daniel L. Akin| title = God on Sex: The Creator's Ideas About Love, Intimacy, and Marriage| year = 2003| publisher = [[B&H Publishing Group]] |pages= 1–291 | isbn = 978-0-8054-2596-3|url=https://books.google.com/books?id=dInbMZK18soC|access-date=October 21, 2015}}</ref> Most Christian views on sexual intercourse are influenced by various interpretations of the [[Bible]].<ref name="Hollinger">{{cite book| author =Dennis P. Hollinger|author-link=Dennis Hollinger|title =The Meaning of Sex: Christian Ethics and the Moral Life|publisher = [[Baker Academic]] | year = 2009 | pages = 30–33 | access-date = December 9, 2014 |isbn = 978-0-8010-3571-5| url =https://books.google.com/books?id=86tzBQAAQBAJ&pg=PA30}}</ref> Sexual intercourse outside of marriage, for example, is considered a [[sin]] in some churches; in such cases, sexual intercourse may be called a sacred covenant, holy, or a holy sacrament between husband and wife.<ref name="Akin"/><ref name="Hollinger"/> Historically, Christian teachings often promoted [[celibacy]],<ref name="Denton">{{cite book| author =Chad Denton|title =The War on Sex: Western Repression from the Torah to Victoria|publisher = [[McFarland & Company|McFarland]] | year = 2014 | pages = 107–117 | access-date = December 9, 2014 |isbn = 978-0-547-20488-8| url =https://books.google.com/books?id=Cl6QBQAAQBAJ&pg=PA107}}</ref> although today usually only certain members (for example, certain [[celibacy of the clergy|religious leaders]]) of some groups take a vow of celibacy, forsaking both marriage and any type of sexual or romantic activity.<ref name="Hollinger"/> The Bible may be interpreted as endorsing penile-vaginal penetration as the only form of acceptable sexual activity,<ref name="Kamitsuka">{{cite book| author =Margaret D. Kamitsuka|title =The Embrace of Eros: Bodies, Desires, and Sexuality in Christianity|publisher = [[Fortress Press]] | year = 2010 | pages = 16–17 | access-date = December 9, 2014 |isbn = 978-1-4514-1351-9| url =https://books.google.com/books?id=VhIrHceA7ssC&pg=PA16}}</ref><ref name="Knauss">{{cite book| author =Stefanie Knauss|title =More Than a Provocation: Sexuality, Media and Theology|publisher = [[Vandenhoeck & Ruprecht]] | year = 2014 | page = 69 | access-date = December 9, 2014 |isbn = 978-3-525-60450-2| url =https://books.google.com/books?id=mv9NAwAAQBAJ&pg=PA69}}</ref> while other interpretations view the Bible as not being clear on oral sex or other particular sexual behaviors and that it is a personal decision as to whether oral sex is acceptable within marriage.<ref name="Kamitsuka"/><ref name="Barnes">{{cite book| author =Robert G. Barnes| author2 =Rosemary J. Barnes|title=Great Sexpectations: Finding Lasting Intimacy in Your Marriage |publisher = [[Zondervan]] | year = 1996 | page = [https://archive.org/details/greatsexpectatio0000barn/page/66 66] | access-date = December 9, 2014 |isbn = 978-0-310-20137-3| url =https://archive.org/details/greatsexpectatio0000barn| url-access =registration}}</ref><ref name="Scheepers">{{cite book| author =Christo Scheepers|publisher = Struik Christian Media|title=Between the Covers: Sexual freedom through the bond of marriage | year = 2012 | page = 53 | access-date = December 9, 2014 |isbn = 978-1-4153-2056-3| url =https://books.google.com/books?id=LJzpAwAAQBAJ&pg=PT53}}</ref> Some sects consider the use of birth control to prevent sexual reproduction a grave sin against God and marriage, as they believe that the main purpose of marriage, or one of its primary purposes, is to produce children, while other sects do not hold such beliefs.<ref name="Oliphant">{{cite book| author =Jill Oliphant|title =OCR Religious Ethics for AS and A2|publisher = [[Routledge]] | year = 2010 | page = 213 | access-date = September 1, 2015 |isbn = 978-1-136-99291-9| url=https://books.google.com/books?id=VmJd87byr1AC&pg=PT213}}</ref>
** In the Roman Catholic Church, if a matrimonial celebration takes place (ratification), but the spouses have not yet engaged in intercourse (consummation), then the marriage is considered to be a marriage via ''[[ratum sed non consummatum]]''. Such a marriage, regardless of the reason for non-consummation, can be dissolved by the [[pope]].<ref name="d'Avray">{{cite book| author =D. L. d'Avray|title =Rationalities in History: A Weberian Essay in Comparison|publisher = [[Cambridge University Press]] | year = 2010 | pages = [https://archive.org/details/rationalitie_dav_2010_000_10426673/page/n188 177]–178 | access-date = September 1, 2015 |isbn = 978-1-139-49050-4| url =https://archive.org/details/rationalitie_dav_2010_000_10426673| url-access =registration}}</ref>
** In [[the Church of Jesus Christ of Latter-day Saints]] (LDS Church) sexual relations within the bonds of matrimony are seen as sacred. Latter-day Saints consider sexual relations to be ordained of God for the creation of children and for the expression of love between husband and wife. Members are discouraged from having any sexual relations before marriage, and from being unfaithful to their spouses after marriage.<ref name="Swatos">{{cite book| author =William H. Swatos| author2 =Peter Kivisto|title=Encyclopedia of Religion and Society|publisher =[[Rowman Altamira]]| year = 1998 | page = 464 | access-date = December 9, 2014 |isbn = 978-0-7619-8956-1| url =https://books.google.com/books?id=6TMFoMFe-D8C&pg=PA464}}</ref>
** [[Shakers]] believe that sexual intercourse is the root of all sin and that all people should therefore be celibate, including married couples. The original Shaker community that peaked at 6,000 full members in 1840 dwindled to [[Sister June Carpenter|three members by 2009]].<ref>{{cite news |title=The Last Ones Standing |author=Chase, Stacey |date=July 23, 2006 |newspaper=[[The Boston Globe]] |url=http://www.boston.com/news/globe/magazine/articles/2006/07/23/the_last_ones_standing/?page=full |archive-url=https://web.archive.org/web/20060813114148/https://www.boston.com/news/globe/magazine/articles/2006/07/23/the_last_ones_standing/?page=full |archive-date=August 13, 2006 |url-status=dead |access-date=July 26, 2023}}</ref>
* In [[Judaism]], a married Jewish man is required to provide his wife with sexual pleasure called ''onah'' (literally, "her time"), which is one of the conditions he takes upon himself as part of the Jewish marriage contract, ''[[ketubah]]'', that he gives her during the Jewish wedding ceremony. In [[Jewish views on marriage]], sexual desire is not evil, but must be satisfied in the proper time, place and manner.<ref name="Zilney">{{cite book| author =Laura J. Zilney| author2 =Lisa Anne Zilney|title=Perverts and Predators: The Making of Sexual Offending Laws|publisher =[[Rowman & Littlefield]]| year = 2009 | pages = [https://archive.org/details/pervertspredator0000ziln/page/7 7]–8| access-date = December 9, 2014 |isbn = 978-0-7425-6624-8| url =https://archive.org/details/pervertspredator0000ziln| url-access =registration}}</ref>
* [[Islam]] views sex within marriage as something pleasurable, a spiritual activity, and a duty.<ref name=columbia/><ref name=islam>Abdul Rahman bin Abdul Karim al-Sheha. Islamic Perspective of Sex (2003) Saudi Arabia. {{ISBN|9960-43-140-1}}</ref><ref name=islam2>Fatima M. D'Oyen. The Miracle of Life. (2007) Islamic Foundation (UK). {{ISBN|0-86037-355-X}}</ref> In Shia Islam, men are allowed to marry upto four wives at a time with whom they can engage in sexual activities, including intercourse.<ref>{{Cite web |date=2015-07-15 |title=Polygamy |url=https://allaboutshias.com/polygamy-2/ |access-date=2024-09-07 |website=All About Shias |language=en-US}}</ref> Shia women are allowed to enter only one marriage at a time, whether temporary or permanent.
* [[Hinduism]] has varied views about sexuality,<ref name="columbia">Don S. Browning, Martha Christian Green, John Witte. Sex, marriage, and family in world religions. (2006) Columbia University Press. {{ISBN|0-231-13116-X}} [https://books.google.com/books?id=qkNE8pRQoboC&pg=PA227]</ref> but according to the [[Kama Sutra]], ''sex'' is considered as a normal activity that is necessary for a fulfilling and happy life.<ref>{{Cite journal |last=Sharma |first=Arvind |author-link=Arvind Sharma |date=1999 |title=The Puruṣārthas: An Axiological Exploration of Hinduism |url=https://www.jstor.org/stable/40018229 |journal=The Journal of Religious Ethics |volume=27 |issue=2 |pages=223–256 |doi=10.1111/0384-9694.00016 |jstor=40018229 |issn=0384-9694}}</ref>
* [[Buddhist]] ethics, in its most general formulation, holds that one should neither be attached to nor crave sensual pleasure since it binds one to the cycle of birth and death, [[samsara]], and prevents one attaining the goal of [[Nirvana]]. Since Buddhist monastics (i.e. [[bhikshu]]s and [[bhikshuni]]s) are to be fully dedicated towards this goal, they undertake the training rule of total abstinence from sexual intercourse, i.e. of celibacy. Other monastic training rules from the Code of Discipline ([[Patimokkha]] or Pratimoksasutra) and canonical [[Vinaya]] scriptures are to prevent masturbation, lustfully touching and speaking to members of the other sex, and other forms of sexual behaviour. Buddhist lay people undertake the [[Five Precepts]], the third of which is avoiding sexual misconduct. [[Peter Harvey (academic)|Peter Harvey]] says that this precept "relates primarily to the avoidance of causing suffering by one's sexual behaviour. Adultery—'going with the wife of another'—is the most straightforward breach of this precept. The wrongness of this is seen as partly in terms of its being an expression of greed, and partly in terms of its harm to others. It is said that a man breaks the precept if he has intercourse with women who are engaged, or who are still protected by any relative, or young girls not protected by a relative, Clearly, rape and incest are breaches of the precept."<ref>[[Peter Harvey (academic)|Harvey, Peter]]. ''An Introduction to Buddhist Ethics: Foundations, Values and Issues''. Cambridge, 2000: 71-72.</ref> The Buddhist Canonical scriptures contain no other regulations or recommendations for lay people—for example, with regards homosexuality, masturbation, sexual practices and contraceptives. However, in keeping with the Buddhist ethical principles of not-harming and avoiding shame, guilt and remorse, socially taboo forms of sexuality as well as obsessive sexual activities can also be seen as being included in the third precept. Later Buddhist authors such as [[Nagarjuna]] give various clarifications and recommendations.<ref>[[Peter Harvey (academic)|Harvey, Peter]]. ''An Introduction to Buddhist Ethics: Foundations, Values and Issues''. Cambridge, 2000: 71-74.</ref>
* In the [[Baháʼí Faith]], sexual relationships are permitted only between a husband and wife.<ref>Kenneth E. Bowers. God Speaks Again: An Introduction to the Baháʼí Faith. (2004) Baháʼí Publishing. {{ISBN|1-931847-12-6}}</ref>
* [[Unitarian Universalist]]s, with an emphasis on strong interpersonal ethics, do not place boundaries on the occurrence of sexual intercourse among consenting adults.<ref>[[John A. Buehrens]] and [[Forrest Church]]. A Chosen Faith: An Introduction to Unitarian Universalism. (1998) Beacon Press. {{ISBN|0-8070-1617-9}}</ref>
* According to the [[Brahma Kumaris]] and [[Prajapita Brahma Kumaris]] religion, the power of [[lust]] is the root of all evil and worse than murder.<ref name="Liz_Hodgkinson_Peace">{{cite book | last = Hodgkinson | first = Liz | author-link = Liz Hodgkinson | title = Peace and Purity: The Story of the Brahma Kumaris a Spiritual Revolution | year = 2002 | publisher = HCI | isbn = 978-1-55874-962-7 | pages = 2–29}}</ref> Purity (celibacy) is promoted for peace and to prepare for life in forthcoming Heaven on earth for 2,500 years when children will be created by the power of the mind.<ref>Babb, Lawrence A. (1987). ''Redemptive Encounters: Three Modern Styles in the Hindu Tradition'' (Comparative Studies in Religion and Society). Oxford University Press. {{ISBN|0-7069-2563-7}}. "Sexual intercourse is unnecessary for reproduction because the souls that enter the world during the first half of the Cycle are in possession of a special yogic power (yog bal) by which they conceive children."</ref><ref>[[David V. Barrett|Barrett, David V]] (2001). The New Believers. Cassell & Co. pp. 265. {{ISBN|0-304-35592-5}}.</ref>
* [[Wicca]]ns are told, as declared within the [[Charge of the Goddess]], to "''[l]et [the Goddess'] worship be within the heart that rejoiceth; for behold, all acts of love and pleasure are [the Goddess'] rituals.''" This statement appears to allow one freedom to explore sensuality and pleasure, and mixed with the final maxim within the [[Wiccan Rede]]—"''26. Eight words the Wiccan Rede fulfill—an' it harm none, do what ye will.''"<ref>[[Lady Gwen Thompson|Thompson, Lady Gwen]]; ''Wiccan-Pagan Potpourri''; Green Egg, №69; Ostara 1974</ref>—Wiccans are encouraged to be responsible with their sexual encounters, in whatever variety they may occur.<ref>[[Hans Holzer]]. The Truth about Witchcraft (1971) Doubleday. page 128. {{ISBN|0-09-004860-1}}</ref>
* [[Meher Baba]] maintained that "In the beginning of married life the partners are drawn to each other by lust as well as love; but with conscious and deliberate cooperation they can gradually lessen the element of lust and increase the element of love. Through this process of sublimation, lust ultimately gives place to deep love."<ref>[[Meher Baba|Baba, Meher]] (1995). ''Discourses''. Myrtle Beach: Sheriar Press. p. 109. {{ISBN|978-1-880619-09-4}}.</ref>

In some cases, the sexual intercourse between two people is seen as contrary to religious law or doctrine. In many religious communities, including the [[Catholic Church]] and [[Bhikkhu|Mahayana Buddhists]], religious leaders are expected to refrain from sexual intercourse in order to devote their full attention, energy, and loyalty to their religious duties.<ref>{{ill|William Skudlarek|de}}. Demythologizing Celibacy: Practical Wisdom from Christian and Buddhist Monasticism. (2008) Liturgical Press. {{ISBN|0-8146-2947-4}}</ref>

==Other animals==
{{Main|Copulation (zoology)|Animal sexual behaviour}}
{{See also|Sexual coercion among animals}}
[[File:Lion sex.jpg|thumb|A pair of [[Lion#Reproduction and life cycle|lions copulating]] in the [[Maasai Mara]], [[Kenya]]]]
[[File:Housefly mating.jpg|thumb|Mating [[Housefly|houseflies]]]]
In [[zoology]], ''copulation'' often means the process in which a male introduces sperm into the female's body, especially directly into her reproductive tract.<ref name="Kent"/><ref name="Copulation1"/> [[Spider]]s have separate male and female sexes. Before mating and copulation, the male spider spins a small web and ejaculates on it. He then stores the sperm in reservoirs on his large [[pedipalp]]s, from which he transfers sperm to the female's genitals. The females can store sperm indefinitely.<ref name="RFB2004Spiders">{{cite book | author=Ruppert, E.E. | author2=Fox, R.S. | author3=Barnes, R.D. | name-list-style=amp | title=Invertebrate Zoology | publisher=Brooks/Cole | edition=7th | isbn=978-0-03-025982-1 | year=2004 | pages=[https://archive.org/details/isbn_9780030259821/page/571 571–584] | chapter=Chelicerata: Araneae | url=https://archive.org/details/isbn_9780030259821/page/571 }}</ref>

Many animals that live in water use [[external fertilization]], whereas [[internal fertilization]] may have developed from a need to maintain [[gamete]]s in a liquid medium in the [[Late Ordovician]] epoch. Internal fertilization with many vertebrates (such as [[reptile]]s, some [[fish]], and most [[bird]]s) occur via [[cloaca]]l copulation (see also [[hemipenis]]), while [[mammal]]s copulate vaginally, and many [[primitive (biology)|basal]] [[vertebrate]]s reproduce sexually with external fertilization.<ref name="Starr">{{cite book| author =Cecie Starr| author2 =Christine Evers| author3 =Lisa Starr|title=Cengage Advantage Books: Biology: A Human Emphasis|publisher =[[Cengage Learning]]| year = 2010 | pages = 630–631| access-date = December 9, 2010 |isbn =978-1-133-17005-1| url =https://books.google.com/books?id=DdU8AAAAQBAJ&pg=PA631}}</ref><ref name="Denecke">{{cite book| author =Edward J. Denecke Jr.|title=New York State Grade 8 Intermediate Level Science Test|publisher =[[Barron's Educational Series]]| year = 2006 | page = 105| access-date = December 9, 2014 |isbn = 978-0-7641-3433-3| url =https://books.google.com/books?id=dbF6g4geyfsC&pg=PA105}}</ref>

For primitive [[insect]]s, the male deposits [[spermatozoa]] on the substrate, sometimes stored within a special structure; [[Courtship display|courtship]] involves inducing the female to take up the sperm package into her genital opening, but there is no actual copulation.<ref name="Yadav">{{cite book| author =M. Yadav|title=Breeding in Insects|publisher =Discovery Publishing House| year = 2003 | page = 59| access-date = December 9, 2014 |isbn = 978-81-7141-737-7| url =https://books.google.com/books?id=ZC5obBYtusEC&pg=PA59}}</ref><ref name="Engelmann">{{cite book| author =Franz Engelmann|title=The Physiology of Insect Reproduction: International Series of Monographs in Pure and Applied Biology: Zoology|publisher =[[Elsevier]]| year = 2013 | pages = 58–59| access-date = December 9, 2014 |isbn = 978-1-4831-8653-5| url =https://books.google.com/books?id=4bXYBAAAQBAJ&pg=PA58}}</ref> In groups that have reproduction similar to spiders, such as [[dragonflies]], males extrude sperm into secondary copulatory structures removed from their genital opening, which are then used to inseminate the female. In dragonflies, it is a set of modified [[sternites]] on the second abdominal segment.<ref name="Leonard">{{cite book| author =Janet Leonard| author2 =Alex Cordoba-Aguilar|title=The Evolution of Primary Sexual Characters in Animals|publisher =[[Oxford University Press]]| year = 2010 | page =334| access-date = December 9, 2014 |isbn = 978-0-19-971703-3| url =https://books.google.com/books?id=PgtXj5R6OfMC&pg=PA334}}</ref> In advanced groups of insects, the male uses its [[aedeagus]], a structure formed from the terminal segments of the abdomen, to deposit sperm directly (though sometimes in a capsule called a ''[[spermatophore]]'') into the female's reproductive tract.<ref name="Gullan">{{cite book| author =P. J. Gullan| author2 =P. S. Cranston|title=The Insects: An Outline of Entomology|publisher =[[John Wiley & Sons]]| year = 2009| page = 124| access-date = December 9, 2014 |isbn = 978-1-4051-4457-5| url =https://books.google.com/books?id=E_6-pGOLUgcC&pg=PA124}}</ref>

Bonobos, chimpanzees and dolphins are species known to engage in heterosexual behaviors even when the female is not in estrus, which is a point in her reproductive cycle suitable for successful impregnation. These species are also known to [[Homosexual behavior in animals|engage in same-sex sexual behaviors]].<ref name="Non-human"/> In these animals, the use of sexual intercourse has evolved beyond reproduction to apparently serve additional social functions (such as bonding).<ref name="Balcombe"/>

==See also==
{{Portal|Human sexuality}}
* [[Human sexual response cycle]]
* [[Mammary intercourse]]
{{clear}}

==References==
{{Reflist|30em}}

==External links==
{{commons|Sexual intercourse in humans|Sexual intercourse}}
* [https://web.archive.org/web/20060112011828/http://www2.hu-berlin.de/sexology/IES/xmain.html The International Encyclopedia of Sexuality]
* Janssen, D. F., [https://web.archive.org/web/20060220110820/http://www2.hu-berlin.de/sexology/GESUND/ARCHIV/GUS/INDEXATLAS.HTM ''Growing Up Sexually. Volume I. World Reference Atlas'']
* [https://web.archive.org/web/20060216005917/http://tidepool.st.usm.edu/crswr/103animalreproduction.html Introduction to Animal Reproduction]
* [https://www.pbs.org/wgbh/evolution/sex/advantage/ Advantages of Sexual Reproduction]
* [[wikt:WikiSaurus:sexual intercourse|Synonyms for sexual intercourse]] – the [[WikiSaurus]] list of synonyms and slang words for sexual intercourse in many languages

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