View source for Sign language

{{short description|Language that uses manual communication and body language to convey meaning}}
{{about|primary sign languages of the deaf|signed versions of spoken languages|manually coded language}}

[[File:ASL family.jpg|thumb|Two men and a woman signing [[American Sign Language]] (2008)]]
[[File:Preservation of the Sign Language (1913).webm|thumb|thumbtime=5|''Preservation of the Sign Language'', George W. Veditz (1913)]]

'''Sign languages''' (also known as '''signed languages''') are [[language]]s that use the visual-manual modality to convey meaning, instead of spoken words. Sign languages are expressed through manual articulation in combination with [[#Non-manual elements|non-manual markers]]. Sign languages are full-fledged natural languages with their own grammar and lexicon.<ref name="SLM" /> Sign languages are not universal and are usually not [[mutual intelligibility|mutually intelligible]],<ref>{{cite web | publisher = Linguistic society |title= What is Sign Language?|url= https://www.linguisticsociety.org/content/what-sign-language|access-date=10 March 2018|url-status=live |archive-url=https://web.archive.org/web/20180213195125/https://www.linguisticsociety.org/content/what-sign-language|archive-date=13 February 2018}}</ref> although there are similarities among different sign languages.

Linguists consider both spoken and signed communication to be types of [[natural language]], meaning that both emerged through an abstract, protracted aging process and evolved over time without meticulous planning.<ref>E.g.: Irit Meir, Wendy Sandler, Carol Padden, and Mark Aronoff (2010): Emerging Sign Languages. In: Marc Marschark and Patricia Elizabeth Spencer (eds.): The Oxford Handbook of Deaf Studies, Language, and Education, Vol. 2, pp. 267–80.</ref> This is supported by the fact that there is substantial overlap between the neural substrates of sign and spoken language processing, despite the obvious differences in modality.<ref>{{Cite journal |last1=Trettenbrein |first1=Patrick C. |last2=Papitto |first2=Giorgio |last3=Friederici |first3=Angela D. |last4=Zaccarella |first4=Emiliano |date=2021-02-15 |title=Functional neuroanatomy of language without speech: An ALE meta‐analysis of sign language |journal=Human Brain Mapping |language=en |volume=42 |issue=3 |pages=699–712 |doi=10.1002/hbm.25254 |issn=1065-9471 |pmc=7814757 |pmid=33118302}}</ref>

Sign language should not be confused with [[body language]], a type of [[non verbal communication|nonverbal communication]]. Linguists also distinguish natural sign languages from other systems that are precursors to them or obtained from them, such as constructed manual codes for spoken languages, [[home sign]], "[[Baby sign language|baby sign]]", and signs learned by non-human primates.

Wherever communities of [[deaf]] people exist, sign languages have developed as useful means of communication and form the core of local [[deaf culture]]s. Although signing is used primarily by the deaf and [[Hearing loss|hard of hearing]], it is also used by hearing individuals, such as those [[Muteness|unable to physically speak]], those who have trouble with oral language due to a disability or condition ([[augmentative and alternative communication]]), and those with deaf family members including [[Child of deaf adult|children of deaf adults]].

The number of sign languages worldwide is not precisely known. Each country generally has its own native sign language; some have more than one. The 2021 edition of ''[[Ethnologue]]'' lists 150 sign languages,<ref>{{citation |contribution = Sign language |title = Ethnologue: Languages of the World |year = 2021 |edition = 24th |publisher = SIL International |access-date = 2021-05-15 |editor1-last = Eberhard |editor1-first = David M. |editor2-last = Simons |editor2-first = Gary F. |editor3-last = Fennig |editor3-first = Charles D. |url = https://www.ethnologue.com/subgroups/sign-language |archive-date = 2019-04-02 |archive-url = https://web.archive.org/web/20190402155824/https://www.ethnologue.com/subgroups/sign-language |url-status = live }}</ref> while the SIGN-HUB Atlas of Sign Language Structures lists over 200 and notes that there are more that have not been documented or discovered yet.<ref>{{citation |title = Atlas of Sign Language Structures |year = 2021 |publisher = Sign-hub |access-date = 2021-01-13 |editor1-last = Hosemann |editor1-first = Jana |editor2-last = Steinbach |editor2-first = Markus |url = https://www.sign-hub.eu/atlas |archive-date = 2021-04-13 |archive-url = https://web.archive.org/web/20210413222932/https://www.sign-hub.eu/atlas |url-status = dead }}</ref> As of 2021, [[Indo-Pakistani Sign Language]] is the most-used sign language in the world, and ''Ethnologue'' ranks it as the 151st most "spoken" language in the world.<ref>[https://www.ethnologue.com/guides/ethnologue200 What are the top 200 most spoken languages?] {{Webarchive|url=https://web.archive.org/web/20230923161950/https://www.ethnologue.com/guides/ethnologue200/ |date=2023-09-23 }}, [[Ethnologue]].</ref>

Some sign languages have obtained some form of [[Legal recognition of sign languages|legal recognition]].<ref>Wheatley, Mark & Annika Pabsch (2012). ''Sign Language Legislation in the European Union – Edition II''. European Union of the Deaf.</ref>

== History ==
{{Main|History of sign language}}
[[Image:Arte para enseñar a hablar a los mudos.jpg|thumb|upright|Juan Pablo Bonet, {{lang|es|Reducción de las letras y arte para enseñar a hablar a los mudos}} ("Reduction of letters and art for teaching mute people to speak") (Madrid, 1620)]]

Groups of deaf people have used sign languages throughout history. One of the earliest written records of a sign language is from the fifth century BC, in [[Plato]]'s ''[[Cratylus (dialogue)|Cratylus]]'', where [[Socrates]] says: "If we hadn't a voice or a tongue, and wanted to express things to one another, wouldn't we try to make signs by moving our hands, head, and the rest of our body, just as dumb people do at present?"<ref name="bauman2008">{{cite book |first=Dirksen |last=Bauman |year=2008 |title=Open your eyes: Deaf studies talking | publisher=University of Minnesota Press |isbn=978-0-8166-4619-7}}</ref> Most of what is known about pre-19th-century sign languages is limited to the manual alphabets (fingerspelling systems) that were invented to facilitate the transfer of words from a spoken language to a sign language, rather than documentation of the language itself.

Debate around European [[monastic sign languages]] developed in the Middle Ages has come to regard them as gestural systems rather than true sign languages.<ref>[https://www.jstor.org/stable/26203846 Stokoe, William C. "Approaching Monastic Sign Language". Sign Language Studies 58 (1988): 37–47] {{Webarchive|url=https://web.archive.org/web/20230127123810/https://www.jstor.org/stable/26203846 |date=2023-01-27 }}; Sayers, Edna Edith [Lois Bragg]. "Visual-Kinetic Communication in Europe Before 1600: A Survey of Sign Lexicons and Finger Alphabets Prior to the Rise of Deaf Education". Journal of Deaf Studies and Deaf Education 2 (1997): 1–25;  [https://www.cambridge.org/core/books/silence-and-sign-language-in-medieval-monasticism/24F1883B33891602C2DAFF8F40B4272B Bruce, Scott G. Silence and Sign Language in Medieval Monasticism: The Cluniac Tradition, C.900–1200. Cambridge Studies in Medieval Life and Thought: Fourth Series. Cambridge: Cambridge University Press, 2007] {{Webarchive|url=https://web.archive.org/web/20230127123256/https://www.cambridge.org/core/books/silence-and-sign-language-in-medieval-monasticism/24F1883B33891602C2DAFF8F40B4272B |date=2023-01-27 }}; [https://www.academia.edu/60144627/_Deafness_and_Nonspeaking_in_Late_Medieval_Iceland_1200_1550_Viator_51_1_2020_311_344 Tirosh, Yoav. "Deafness and Nonspeaking in Late Medieval Iceland (1200–1550)," Viator 51.1 (2020): 311-344] {{Webarchive|url=https://web.archive.org/web/20230127122031/https://www.academia.edu/60144627/_Deafness_and_Nonspeaking_in_Late_Medieval_Iceland_1200_1550_Viator_51_1_2020_311_344 |date=2023-01-27 }}</ref> Monastic sign languages were the basis for the first known manual alphabet used in deaf schools, developed by [[Pedro Ponce de León]].<ref name="Nielsen 2012">{{Cite book |last=Nielsen |first=Kim |author-link=Kim E. Nielsen |url= |title=A Disability History of the United States |publisher=Beacon Press |year=2012 |isbn=978-080702204-7 |location=Boston, Massachusetts |pages=}}</ref>
[[File:Alphabets - Ghanaian Sign Language.webm|thumb|Alphabets - Ghanaian Sign Language]]

The earliest records of contact between Europeans and Indigenous peoples of the Gulf Coast region in what is now Texas and northern Mexico note a fully formed sign language already in use by the time of the Europeans' arrival there.<ref name="Wurtzburg and Campbell">Wurtzburg, Susan, and Campbell, Lyle. "North American Indian Sign Language: Evidence for its Existence before European Contact," ''International Journal of American Linguistics,'' Vol. 61, No. 2 (Apr., 1995), pp. 153-167.</ref> These records include the accounts of [[Cabeza de Vaca]] in 1527 and [[Francisco Vásquez de Coronado|Coronado]] in 1541.

In 1620, [[Juan Pablo Bonet]] published {{lang|es|Reducción de las letras y arte para enseñar a hablar a los mudos}} ('Reduction of letters and art for teaching mute people to speak') in Madrid.<ref>Pablo Bonet, J. de (1620) ''Reduction de las letras y Arte para enseñar á ablar los Mudos''. Ed. Abarca de Angulo, Madrid, ejemplar facsímil accesible en la {{cite web|title=Reduction de las letras y arte para enseñar a ablar los mudos|url=http://www.cervantesvirtual.com/obra-visor/reduccion-de-las-letras-y-arte-para-ensenar-a-hablar-a-los-mudos--0/html/ff9182e0-82b1-11df-acc7-002185ce6064.htm|url-status=live|archive-url=https://web.archive.org/web/20211004150037/http://www.cervantesvirtual.com:80/obra-visor/reduccion-de-las-letras-y-arte-para-ensenar-a-hablar-a-los-mudos--0/html/|archive-date=2021-10-04|access-date=2021-10-17|website=[[Miguel de Cervantes Virtual Library]]}}, online (Spanish) scan of book.</ref> It is considered the first modern treatise of sign language phonetics, setting out a method of oral education for deaf people and a manual alphabet.

[[File:Jbulwer.jpg|upright|thumb|Chirogram from ''Chirologia'', 1644]]
In Britain, manual alphabets were also in use for a number of purposes, such as secret communication,<ref>Wilkins, John (1641). ''Mercury, the Swift and Silent Messenger''. The book is a work on cryptography, and fingerspelling was referred to as one method of "secret discoursing, by signes and gestures".  Wilkins gave an example of such a system: "Let the tops of the fingers signifie the five vowels; the middle parts, the first five consonants; the bottomes of them, the five next consonants; the spaces betwixt the fingers the foure next.  One finger laid on the side of the hand may signifie T.  Two fingers V the consonant; Three W.  The little finger crossed X.  The wrist Y.  The middle of the hand Z." (1641:116–117)</ref> public speaking, or communication by or with deaf people.<ref>John Bulwer's "Chirologia: or the natural language of the hand.", published in 1644, London, mentions that alphabets are in use by deaf people, although Bulwer presents a different system which is focused on public speaking.</ref> In 1648, [[John Bulwer]] described "Master Babington", a deaf man proficient in the use of a manual alphabet, "{{Not a typo|contryved}} on the {{Not a typo|joynts}} of his fingers", whose wife could converse with him easily, even in the dark through the use of [[tactile signing]].<ref>Bulwer, J. (1648) ''Philocopus, or the Deaf and Dumbe Mans Friend'', London: Humphrey and Moseley.</ref>

In 1680, [[George Dalgarno]] published ''Didascalocophus, or, The deaf and dumb mans tutor'',<ref>Dalgarno, George. ''Didascalocophus, or, The deaf and dumb mans tutor''. Oxford: Halton, 1680.</ref> in which he presented his own method of deaf education, including an "arthrological" alphabet, where letters are indicated by pointing to different joints of the fingers and palm of the left hand. Arthrological systems had been in use by hearing people for some time;<ref>See Wilkins (1641) above. Wilkins was aware that the systems he describes are old, and refers to Bede's account of Roman and Greek finger alphabets.</ref> some have speculated that they can be traced to early [[Ogham]] manual alphabets.<ref>{{cite web |url=http://www.bris.ac.uk/Depts/DeafStudiesTeaching/bslsoc/Sessions/s9.htm |title=Session 9 |publisher=Bris.ac.uk |date=2000-11-07 |access-date=2010-09-28 |url-status=live |archive-url=https://web.archive.org/web/20100602102335/http://www.bris.ac.uk/Depts/DeafStudiesTeaching/bslsoc/Sessions/s9.htm |archive-date=2010-06-02 }}</ref><ref>{{cite journal|author=Montgomery, G.|title=The Ancient Origins of Sign Handshapes|journal=Sign Language Studies|volume=2|issue=3|year=2002|pages=322–334|doi=10.1353/sls.2002.0010|jstor=26204860|s2cid=144243540|url=https://www.jstor.org/stable/pdf/26204860.pdf|access-date=2021-04-15|archive-date=2023-01-04|archive-url=https://web.archive.org/web/20230104091153/https://www.jstor.org/stable/26204860|url-status=live}}</ref>

The [[vowel]]s of this alphabet have survived in the modern alphabets used in [[British Sign Language]], [[Auslan]] and [[New Zealand Sign Language]]. The earliest known printed pictures of consonants of the modern [[two-handed alphabet]] appeared in 1698 with {{Lang|la|Digiti Lingua}} (Latin for ''Language'' [or ''Tongue''] ''of the Finger''), a pamphlet by an anonymous author who was himself unable to speak.<ref>{{cite journal|last1=Moser|first1=Henry M.|last2=O'Neill|first2=John J.|last3=Oyer|first3=Herbert J.|last4=Wolfe|first4=Susan M.|last5=Abernathy|first5=Edward A.|last6=Schowe|first6=Ben M.|title=Historical Aspects of Manual Communication|journal=Journal of Speech and Hearing Disorders|volume=25|issue=2|year=1960|pages=145–151|doi=10.1044/jshd.2502.145|pmid=14424535}}</ref><ref>Hay, A. and Lee, R. (2004) ''A Pictorial History of the evolution of the British Manual Alphabet''. British Deaf History Society Publications: Middlesex</ref> He suggested that the manual alphabet could also be used by mutes, for silence and secrecy, or purely for entertainment. Nine of its letters can be traced to earlier alphabets, and 17 letters of the modern two-handed alphabet can be found among the two sets of 26 handshapes depicted.

[[Charles de La Fin]] published a book in 1692 describing an alphabetic system where pointing to a body part represented the first letter of the part (e.g. Brow=B), and vowels were located on the fingertips as with the other British systems.<ref>Charles de La Fin (1692). ''Sermo mirabilis, or, The silent language whereby one may learn ... how to impart his mind to his friend, in any language ... being a wonderful art kept secret for several ages in Padua, and now published only to the wise and prudent ...'' London, Printed for Tho. Salusbury... and sold by Randal Taylor... 1692. {{OCLC|27245872}}</ref> He described such codes for both English and Latin.

By 1720, the British manual alphabet had found more or less its present form.<ref>Daniel Defoe (1720). "The Life and Adventures of Mr. Duncan Campbell"</ref> Descendants of this alphabet have been used by deaf communities, at least in education, in the former British colonies India, Australia, New Zealand, Uganda and South Africa, as well as the republics and provinces of the former Yugoslavia, Grand Cayman Island in the Caribbean, Indonesia, Norway, Germany and the United States.

During the [[Polygar war|Polygar Wars]] against the British, [[Veeran Sundaralingam]] communicated with [[Veerapandiya Kattabomman]]'s mute younger brother, [[Oomaithurai]], by using their own sign language.{{Clarify|reason=grammar needs work|date=August 2021}}

Frenchman [[Abbé de l'Épée|Charles-Michel de l'Épée]] published his manual alphabet in the 18th century, which has survived largely unchanged in France and North America until the present time. In 1755, Abbé de l'Épée founded the first school for deaf children in Paris; [[Laurent Clerc]] was arguably its most famous graduate. Clerc went to the United States with [[Thomas Hopkins Gallaudet]] to found the [[American School for the Deaf]] in Hartford, Connecticut, in 1817.<ref>Canlas, Loida (2006). [https://web.archive.org/web/20060903131510/http://clerccenter.gallaudet.edu/Literacy/MSSDLRC/clerc/ "Laurent Clerc: Apostle to the Deaf People of the New World"]. The Laurent Clerc National Deaf Education Center, Gallaudet University.</ref><ref name=":1">{{Cite web |date=2014-02-06 |title=How Sign Language Works |url=https://www.stuffyoushouldknow.com/podcasts/sign-language-works.htm |url-status=dead |archive-url=https://web.archive.org/web/20181102153517/https://www.stuffyoushouldknow.com/podcasts/sign-language-works.htm |archive-date=2018-11-02 |access-date=2019-03-26 |website=[[Stuff You Should Know]] |language=en}}</ref> Gallaudet's son, [[Edward Miner Gallaudet]], founded a school for the deaf in 1857 in Washington, D.C., which in 1864 became the National Deaf-Mute College. Now called [[Gallaudet University]], it is still the only liberal arts university for deaf people in the world.

[[International Sign]], formerly known as Gestuno, is used mainly at international deaf events such as the [[Deaflympics]] and meetings of the [[World Federation of the Deaf]]. While recent studies claim that International Sign is a kind of a [[pidgin]], they conclude that it is more complex than a typical pidgin and indeed is more like a full sign language.<ref>Cf. Supalla, Ted & Rebecca Webb (1995). "The grammar of international sign: A new look at pidgin languages." In: [[Karen Emmorey|Emmorey, Karen]] & Judy Reilly (eds). ''Language, gesture, and space.'' (International Conference on Theoretical Issues in Sign Language Research) Hillsdale, N.J.: Erlbaum, pp. 333–352</ref><ref name=kee/> While the more commonly used term is International Sign, it is sometimes referred to as '''Gestuno''',<ref>Rubino, F., Hayhurst, A., and Guejlman, J. (1975). ''Gestuno. International sign language of the deaf.'' Carlisle: British Deaf Association.</ref> '''International Sign Pidgin'''<ref name="kee">{{cite journal|last1=McKee|first1=Rachel|last2=Napier|first2=Jemina|title=Interpreting into International Sign Pidgin|journal=Sign Language & Linguistics|volume=5|issue=1|year=2002|pages=27–54|url=https://www.researchgate.net/publication/233659867|doi=10.1075/sll.5.1.04mck|access-date=2021-04-15|archive-date=2024-05-26|archive-url=https://web.archive.org/web/20240526073548/https://www.researchgate.net/publication/233659867_Interpreting_into_International_Sign_Pidgin_An_analysis|url-status=live}}</ref> or '''International Gesture''' (IG).<ref>Bar-Tzur, David (2002). ''International gesture: Principles and gestures'' [http://www.theinterpretersfriend.com/indj/ig.html website] {{Webarchive|url=https://web.archive.org/web/20171111191723/http://www.theinterpretersfriend.com/indj/ig.html |date=2017-11-11 }}<br />Moody, W. (1987).''International gesture.'' In J. V. Van Cleve (ed.), "Gallaudet encyclopedia of deaf people and deafness", Vol 3 S-Z, Index. New York: McGraw-Hill Book Company Inc.</ref> International Sign is a term used by the [[World Federation of the Deaf]] and other international organisations.

== Linguistics ==
Sign languages have capability and complexity equal to spoken languages; their study as part of the field of [[linguistics]] has demonstrated that they exhibit the fundamental properties that exist in all languages.<ref name=klima>[[Edward Klima|Klima, Edward S.]]; & [[Ursula Bellugi|Bellugi, Ursula]]. (1979). ''The signs of language''. Cambridge, MA: Harvard University Press. {{ISBN|0-674-80795-2}}.</ref><ref name="SLM">Sandler, Wendy; & Lillo-Martin, Diane. (2006). Sign Language and Linguistic Universals. Cambridge: Cambridge University Press.</ref><ref>{{cite book|last1=Baker|first1=Anne|last2=Bogaerde|first2=Beppie van den|last3=Pfau|first3=Roland|first4=G. M.|last4=Schermer|title=The Linguistics of Sign Languages: An Introduction|url=https://books.google.com/books?id=kC01jwEACAAJ|year=2016|publisher=John Benjamins Publishing Company|isbn=978-90-272-1230-6|page=2|access-date=2021-04-15|archive-date=2023-01-14|archive-url=https://web.archive.org/web/20230114125750/https://books.google.com/books?id=kC01jwEACAAJ|url-status=live}}</ref> Such fundamental properties include [[duality of patterning]]<ref>Stokoe, William C. 1960. [http://saveourdeafschools.org/stokoe_1960.pdf Sign Language Structure: An Outline of the Visual Communication Systems of the American Deaf] {{Webarchive|url=https://web.archive.org/web/20131202224634/http://saveourdeafschools.org/stokoe_1960.pdf |date=2013-12-02 }}, ''Studies in linguistics: Occasional papers (No. 8)''. Buffalo: Dept. of Anthropology and Linguistics, University of Buffalo.</ref> and [[recursion]].<ref>Bross, Fabian (2020). The clausal syntax of German Sign Language. A cartographic approach. Berlin: Language Science Press. Page 37-38.</ref> Duality of patterning means that languages are composed of smaller, meaningless units which can be combined into larger units with meaning (see below). The term recursion means that languages exhibit grammatical rules and the output of such a rule can be the input of the same rule. It is, for example, possible in sign languages to create [[subordinate clause]]s and a subordinate clause may contain another subordinate clause.

Sign languages are not [[mime]]—in other words, signs are conventional, often arbitrary and do not necessarily have a visual relationship to their referent, much as most spoken language is not [[onomatopoeic]]. While [[iconicity]] is more systematic and widespread in sign languages than in spoken ones, the difference is not categorical.<ref>[[Trevor Johnston|Johnston, Trevor]] A. (1989). [https://web.archive.org/web/20080726084538/http://homepage.mac.com/trevor.a.johnston/dissertation.htm  ''Auslan: The Sign Language of the Australian Deaf community'']. The University of Sydney: unpublished Ph.D. dissertation.</ref> The visual modality allows the human preference for close connections between form and meaning, present but suppressed in spoken languages, to be more fully expressed.<ref name="Taub 2001"/>

Sign languages, like spoken languages, organize elementary, meaningless units into meaningful [[semantic]] units. This type of organization in natural language is often called [[duality of patterning]]. As in spoken languages, these meaningless units are represented as (combinations of) [[Feature (linguistics)|features]], although coarser descriptions are often also made in terms of five "parameters": [[handshape]] (or ''handform''), [[Orientation (sign language)|orientation]], [[Location (sign language)|location]] (or ''place of articulation''), [[Movement (sign language)|movement]], and non-manual [[Expression (sign language)|expression]]. These meaningless units in sign languages were initially called [[chereme]]s,<ref>Fabian Bross (2016). [https://www.researchgate.net/publication/317336147_Chereme_In_Hall_T_A_Pompino-Marschall_B_ed_Dictionaries_of_Linguistics_and_Communication_Science_Worterbucher_zur_Sprach-_und_Kommunikationswissenschaft_WSK_Volume_Phonetics_and_Phonology_Berlin_New_Y "Chereme"] {{webarchive |url=https://web.archive.org/web/20180317231914/https://www.researchgate.net/publication/317336147_Chereme_In_Hall_T_A_Pompino-Marschall_B_ed_Dictionaries_of_Linguistics_and_Communication_Science_Worterbucher_zur_Sprach-_und_Kommunikationswissenschaft_WSK_Volume_Phonetics_and_Phonology_Berlin_New_Y |date=2018-03-17 }}. In: Hall, T. A. Pompino-Marschall, B. (ed.): Dictionaries of Linguistics and Communication Science. Volume: Phonetics and Phonology. Berlin, New York: Mouton de Gruyter.</ref> from the Greek word for ''hand'', by analogy to the [[phoneme]]s, from Greek for ''voice'', of spoken languages. Now they are sometimes called phonemes when describing sign languages too, since the function is the same, but more commonly discussed in terms of "features"<ref name="SLM" /> or "parameters".<ref>{{cite web |last1=Vicars |first1=Bill |title=American Sign Language: "parameters" |url=https://www.lifeprint.com/asl101/pages-layout/parameters.htm#:~:text=Note%20if%20you%20are%20taking,%2C%20movement%2C%20and%20palm%20orientation. |website=ASL University |publisher=Bill Vicars |access-date=2021-08-13 |archive-date=2021-11-29 |archive-url=https://web.archive.org/web/20211129115338/https://www.lifeprint.com/asl101/pages-layout/parameters.htm#:~:text=Note%20if%20you%20are%20taking,%2C%20movement%2C%20and%20palm%20orientation. |url-status=live }}</ref> More generally, both sign and spoken languages share the [[Hockett's design features|characteristics]] that linguists have found in all natural human languages, such as transitoriness, [[semanticity]], [[arbitrariness]], [[Productivity (linguistics)|productivity]], and [[Traditional transmission|cultural transmission]].{{Clarify|reason=further explanation of what is meant by these terms is needed|date=June 2019}}

Common linguistic features of many sign languages are the occurrence of [[Classifier constructions in sign languages|classifier constructions]], a high degree of [[inflection]] by means of changes of movement, and a [[Topic-comment language|topic-comment]] [[syntax]]. More than spoken languages, sign languages can convey meaning by simultaneous means, e.g. by the use of [[Signing space|space]], two manual articulators, and the signer's face and body. Though there is still much discussion on the topic of iconicity in sign languages, classifiers are generally considered to be highly iconic, as these complex constructions "function as predicates that may express any or all of the following: motion, position, stative-descriptive, or handling information".<ref>Emmorey, K. (2002). ''Language, cognition and the brain: Insights from sign language research''. Mahwah, NJ: Lawrence Erlbaum Associates.</ref> It needs to be noted that the term classifier is not used by everyone working on these constructions. Across the field of sign language linguistics the same constructions are also referred with other terms such as depictive signs.

Today, linguists study sign languages as true languages, part of the field of linguistics. However, the category "sign languages" was not added to the [[Linguistic Bibliography|''Linguistic Bibliography/Bibliographie Linguistique'']] until the 1988 volume,<ref>{{cite book |pages=970–972 |title=Linguistic Bibliography for the Year 1988 |year=1990 |isbn=978-07-92-30936-9 |place=Leiden, Netherlands |publisher=Brill |editor1=Janse, Mark |editor2=Borkent, Hans |editor3=Tol, Sijmen}}</ref> when it appeared with 39 entries.

=== Relationships with spoken languages ===
[[Image:Holečkova, nápis ve znakové řeči.jpg|thumb| Sign language relief sculpture on a stone wall: "Life is beautiful, be happy and love each other", by Czech sculptor [[Zuzana Čížková]] on Holečkova Street in [[Prague]]-[[Smíchov]], by a school for the deaf]]

There is a common misconception<ref>{{Cite journal |last1=Pirot |first1=Khunaw Sulaiman |last2=Ali |first2=Wrya Izaddin |date=2021-09-29 |title=The Common Misconceptions about Sign Language |url=http://journal.uor.edu.krd/index.php/JUR/article/view/629 |journal=Journal of University of Raparin |volume=8 |issue=3 |pages=110–132 |doi=10.26750/Vol(8).No(3).Paper6 |s2cid=244246983 |issn=2522-7130 |doi-access=free |access-date=2022-09-26 |archive-date=2022-12-04 |archive-url=https://web.archive.org/web/20221204075309/http://journal.uor.edu.krd/index.php/JUR/article/view/629 |url-status=live }}</ref> that sign languages are [[manually coded language|spoken language expressed in signs]], or that they were invented by hearing people.<ref>{{cite web|last=Perlmutter|first=David M.|title=What is Sign Language?|url=http://www.linguisticsociety.org/files/Sign_Language.pdf|work=LSA|access-date=4 November 2013|url-status=live|archive-url=https://web.archive.org/web/20140412004710/http://www.linguisticsociety.org/files/Sign_Language.pdf|archive-date=12 April 2014}}</ref> Similarities in [[Sign language in the brain|language processing in the brain]] between signed and spoken languages further perpetuated this misconception. Hearing teachers in deaf schools, such as Charles-Michel de l'Épée or Thomas Hopkins Gallaudet, are often incorrectly referred to as "inventors" of sign language. Instead, sign languages, like all natural languages, are developed by the people who use them, in this case, deaf people, who may have little or no knowledge of any spoken language.

As a sign language develops, it sometimes borrows elements from spoken languages, just as all languages borrow from other languages that they are in contact with. Sign languages vary in how much they borrow from spoken languages. In many sign languages, a manual alphabet ("fingerspelling") may be used in signed communication to borrow a word from a spoken language. This is most commonly used for proper names of people and places; it is also used in some languages for concepts for which no sign is available at that moment, particularly if the people involved are to some extent bilingual in the spoken language. Fingerspelling can sometimes be a source of new signs, such as initialized signs, in which the handshape represents the first letter of a spoken word with the same meaning.
[[File:Keep Wales Safe This Winter- British Sign Language (BSL).webm|thumb|A January 2021 [[Welsh Government]] video informing viewers of their new [[COVID-19 pandemic in Wales|COVID-19]] regulations]]

On the whole, though, sign languages are independent of spoken languages and follow their own paths of development. For example, [[British Sign Language]] (BSL) and [[American Sign Language]] (ASL) are quite different and mutually unintelligible, even though the hearing people of the United Kingdom and the United States share the same spoken language. The grammars of sign languages do not usually resemble those of spoken languages used in the same geographical area; in fact, in terms of syntax, ASL shares more with spoken [[Japanese grammar|Japanese]] than it does with English.<ref>[[Karen Nakamura|Nakamura, Karen]]. (1995). "About American Sign Language." Deaf Resource Library, Yale University. [http://www.deaflibrary.org/asl.html] {{Webarchive|url=https://web.archive.org/web/20130519230633/http://www.deaflibrary.org/asl.html|date=2013-05-19}}</ref>

Similarly, countries which use a single spoken language throughout may have two or more sign languages, or an area that contains more than one spoken language might use only one sign language. [[South Africa]], which has 11 official spoken languages and a similar number of other widely used spoken languages, is a good example of this. It has only one sign language with two variants due to its history of having two major educational institutions for the deaf which have served different geographic areas of the country.

=== Spatial grammar and simultaneity ===
[[File:Hello1.ogv|thumb|''Hello'' in ASL (American Sign Language)]]
[[File:Hello2.ogv|thumb|Another variation of ''hello'' in ASL (American Sign Language)]]
Sign languages exploit the unique features of the visual medium (sight), but may also exploit tactile features ([[Tactile signing|tactile sign languages]]). Spoken language is by and large linear; only one sound can be made or received at a time. Sign language, on the other hand, is visual and, hence, can use a simultaneous expression, although this is limited articulatorily and linguistically. Visual perception allows processing of simultaneous information.

One way in which many sign languages take advantage of the spatial nature of the language is through the use of classifiers. [[Classifier constructions in sign languages|Classifiers]] allow a signer to spatially show a referent's type, size, shape, movement, or extent.

The possible simultaneity of sign languages in contrast to spoken languages is sometimes exaggerated. The use of two manual articulators is subject to motor constraints, resulting in a large extent of symmetry<ref>Battison, Robbin (1978). ''Lexical Borrowing in American Sign Language.'' Silver Spring, MD: Linstok Press.</ref> or signing with one articulator only. Further, sign languages, just like spoken languages, depend on linear sequencing of signs to form sentences; the greater use of simultaneity is mostly seen in the [[Morphology (linguistics)|morphology]] (internal structure of individual signs).

=== Non-manual elements ===
{{main|Nonmanual feature}}
Sign languages convey much of their [[prosody (linguistics)|prosody]] through non-manual elements. Postures or movements of the body, head, eyebrows, eyes, cheeks, and mouth are used in various combinations to show several categories of information, including [[lexical item|lexical]] distinction, [[grammar|grammatical]] structure, [[adjective|adjectival]] or [[adverb]]ial content, and [[discourse]] functions.

At the lexical level, signs can be lexically specified for non-manual elements in addition to the manual articulation. For instance, facial expressions may accompany verbs of emotion, as in the sign for ''angry'' in [[Czech Sign Language]]. Non-manual elements may also be lexically contrastive. For example, in ASL (American Sign Language), facial components distinguish some signs from other signs. An example is the sign translated as ''not yet'', which requires that the tongue touch the lower lip and that the head rotate from side to side, in addition to the manual part of the sign. Without these features the sign would be interpreted as ''late''.<ref>Liddell, Scott K. (2003). ''Grammar, Gesture, and Meaning in American Sign Language.'' Cambridge: Cambridge University Press.</ref> [[Mouthing]]s, which are (parts of) spoken words accompanying lexical signs, can also be contrastive, as in the manually identical signs for ''doctor'' and ''battery'' in [[Dutch Sign Language|Sign Language of the Netherlands]].<ref>{{Cite book |title=SignGram blueprint: A guide to sign language grammar writing |publisher=De Gruyter Mouton |editor1=Josep Quer i Carbonell |editor2=Carlo Cecchetto |editor3=Rannveig Sverrisd Ãttir |year=2017 |isbn=9781501511806 |oclc=1012688117}}</ref>

While the content of a signed sentence is produced manually, many grammatical functions are produced non-manually (i.e., with the face and the torso).<ref>{{cite journal | last1 = Bross | first1 = Fabian | last2 = Hole | first2 = Daniel | title = Scope-taking strategies in German Sign Language | journal = Glossa | volume = 2 | issue = 1| pages = 1–30 | doi = 10.5334/gjgl.106 | doi-access = free }}</ref> Such functions include questions, negation, relative clauses and topicalization.<ref>{{cite journal|last=Boudreault|first=Patrick|author2=Mayberry, Rachel I.|year=2006|title=Grammatical processing in American Sign Language: Age of first-language acquisition effects in relation to syntactic structure|journal=Language and Cognitive Processes|volume=21|issue=5|pages=608–635|doi=10.1080/01690960500139363|s2cid=13572435}}</ref> ASL and BSL use similar non-manual marking for yes/no questions, for example. They are shown through raised eyebrows and a forward head tilt.<ref name="Baker&Cokely">Baker, Charlotte, and Dennis Cokely (1980). ''American Sign Language: A teacher's resource text on grammar and culture.'' Silver Spring, MD: T.J. Publishers.</ref><ref name="Sutton-Spence&Woll">Sutton-Spence, Rachel, and Bencie Woll (1998). ''The linguistics of British Sign Language.'' Cambridge: Cambridge University Press.</ref>

Some adjectival and adverbial information is conveyed through non-manual elements, but what these elements are varies from language to language. For instance, in ASL a slightly open mouth with the tongue relaxed and visible in the corner of the mouth means "carelessly", but a similar non-manual in BSL means "boring" or "unpleasant".<ref name=Sutton-Spence&Woll />

Discourse functions such as [[conversation analysis|turn taking]] are largely regulated through head movement and eye gaze. Since the addressee in a signed conversation must be watching the signer, a signer can avoid letting the other person have a turn by not looking at them, or can indicate that the other person may have a turn by making eye contact.<ref>Baker, Charlotte (1977). Regulators and turn-taking in American Sign Language discourse, in Lynn Friedman, ''On the other hand: New perspectives on American Sign Language.'' New York: Academic Press. {{ISBN|9780122678509}}</ref>

=== Iconicity ===
[[Iconicity]] is similarity or analogy between the form of a sign (linguistic or otherwise) and its meaning, as opposed to [[Arbitrariness#Linguistics|arbitrariness]].<ref>{{cite journal |last1=Bross|first1=F. |year=2024 |title=What is iconicity? |journal=Sign Language & Linguistics |volume=27 |issue=1 |pages=73–102 |doi=10.1075/sll.22003.bro |url=https://lingbuzz.net/lingbuzz/008405}}</ref> The first studies on iconicity in ASL were published in the late 1970s and early 1980s.  Many early sign language linguists rejected the notion that iconicity was an important aspect of sign languages, considering most perceived iconicity to be extralinguistic.<ref name=":2"/><ref name=klima/> However, mimetic aspects of sign language (signs that imitate, mimic, or represent) are found in abundance across a wide variety of sign languages. For example, when deaf children learning sign language try to express something but do not know the associated sign, they will often invent an iconic sign that displays mimetic properties.<ref>{{cite journal|author1=Klima, Edward|author2= Bellugi, Ursula|title=The Signs of Language|journal= Sign Language Studies|volume= 1062|issue=1|year= 1989|pages=  11}}</ref> Though it never disappears from a particular sign language, iconicity is gradually weakened as forms of sign languages become more customary and are subsequently grammaticized. As a form becomes more conventional, it becomes disseminated in a methodical way phonologically to the rest of the sign language community.<ref>Brentari, Diane. "Introduction." Sign Languages, 2011, pp. 12.</ref> Nancy Frishberg concluded that though originally present in many signs, iconicity is degraded over time through the application of natural grammatical processes.<ref name=":2" />

In 1978, psychologist [[Roger Brown (psychologist)|Roger Brown]] was one of the first to suggest that the properties of ASL give it a clear advantage in terms of learning and memory.<ref>{{cite journal | last1 = Brown | first1 = R | year = 1978 | title = Why Are Signed Languages Easier to Learn than Spoken Languages? Part Two | journal = Bulletin of the American Academy of Arts and Sciences | volume = 32 | issue = 3| pages = 25–44 | doi = 10.2307/3823113 | jstor = 3823113 }}</ref>  In his study, Brown found that when a group of six hearing children were taught signs that had high levels of iconic mapping they were significantly more likely to recall the signs in a later memory task than another group of six children that were taught signs that had little or no iconic properties. In contrast to Brown, linguists [[Elissa L. Newport|Elissa Newport]] and Richard Meier found that iconicity "appears to have virtually no impact on the acquisition of American Sign Language".<ref>{{Cite book|title=The crosslinguistic study of language acquisition|last1=Newport|first1=Elissa|last2=Meier|first2=Richard|publisher=Lawrence Erlbaum Associates|year=1985|isbn=0898593670|pages=[https://archive.org/details/crosslinguistics0001unse/page/881 881–938]|url=https://archive.org/details/crosslinguistics0001unse/page/881}}</ref>

A central task for the pioneers of sign language linguistics was trying to prove that ASL was a real language and not merely a collection of gestures or "English on the hands." One of the prevailing beliefs at this time was that "real languages" must consist of an arbitrary relationship between form and meaning. Thus, if ASL consisted of signs that had iconic form-meaning relationship, it could not be considered a real language. As a result, iconicity as a whole was largely neglected in research of sign languages for a long time. However, iconicity also plays a role in many spoken languages. Spoken [[Japanese language|Japanese]] for example exhibits many words mimicking the sounds of their potential referents (see [[Japanese sound symbolism]]). Later researchers, thus, acknowledged that natural languages do not need to consist of an arbitrary relationship between form and meaning.<ref>For the history of research on iconicity in sign languages see, for example: Vermeerbergen, Myriam (2006): Past and current trends in sign language research. In: Language & Communication, 26(2). 168-192.</ref> The visual nature of sign language simply allows for a greater degree of iconicity compared to spoken languages as most real-world objects can be described by a prototypical shape (e.g., a table usually has a flat surface), but most real-world objects do not make prototypical sounds that can be mimicked by spoken languages (e.g., tables do not make prototypical sounds). It has to be noted, however, that sign languages are not fully iconic. On the one hand, there are also many arbitrary signs in sign languages and, on the other hand, the grammar of a sign language puts limits to the degree of iconicity: All known sign languages, for example, express lexical concepts via manual signs. From a truly iconic language one would expect that a concept like smiling would be expressed by mimicking a smile (i.e., by performing a smiling face). All known sign languages, however, do not express the concept of smiling by a smiling face, but by a manual sign.<ref>Bross, Fabian (2020). The clausal syntax of German Sign Language. A cartographic approach. Berlin: Language Science Press. Page 25.</ref>

The [[cognitive linguistics]] perspective rejects a more traditional definition of iconicity as a relationship between linguistic form and a concrete, real-world referent. Rather it is a set of selected correspondences between the form and meaning of a sign.<ref name="Taub 2001">Taub, S. (2001). ''Language from the body''. New York : Cambridge University Press.</ref> In this view, iconicity is grounded in a language user's mental representation ("[[construal]]" in [[cognitive grammar]]). It is defined as a fully grammatical and central aspect of a sign language rather than a peripheral phenomenon.<ref name="Wilcox 2004"/>

The cognitive linguistics perspective allows for some signs to be fully iconic or partially iconic given the number of correspondences between the possible parameters of form and meaning.<ref name="Wilcox 2000"/> In this way, the [[Israeli Sign Language]] (ISL) sign for ''ask'' has parts of its form that are iconic ("movement away from the mouth" means "something coming from the mouth"), and parts that are arbitrary (the handshape, and the orientation).<ref name="Meir 2010"/>

Many signs have [[metaphoric]] mappings as well as iconic or metonymic ones. For these signs there are three-way correspondences between a form, a concrete source and an abstract target meaning. The ASL sign LEARN has this three-way correspondence. The abstract target meaning is "learning". The concrete source is putting objects into the head from books. The form is a grasping hand moving from an open palm to the forehead. The iconic correspondence is between form and concrete source. The metaphorical correspondence is between concrete source and abstract target meaning. Because the concrete source is connected to two correspondences linguistics refer to metaphorical signs as "double mapped".<ref name="Taub 2001"/><ref name="Wilcox 2000"/><ref name="Meir 2010"/>
{{Clear}}

=== Classification ===
{{See also|List of sign languages}}
[[File:Sign language families.svg|thumb|300px|alt=Sign language families I|'''The classification of Sign Language families'''
{{Legend|#5d6a8f|[[French Sign Language family]]}}
{{Legend|#1e2f5d|→[[American Sign Language]] (ASL) cluster}}
{{Legend|#93a1c7|→[[Russian Sign Language]] cluster}}
{{Legend|#a8d3db|→[[Czech Sign Language]] cluster}}
{{Legend|#9c6cd0|[[Danish Sign Language]] family}}
{{Legend|#a596d8|[[Swedish Sign Language family]]}}
{{Legend|#b08660|[[German Sign Language family]]}}
{{Legend|#660066|[[Vietnamese sign languages]] & some Thai and Lao SLs}}
{{Legend|#383834|[[Arab sign-language family]]}}
{{Legend|#99ff00|[[Indo-Pakistani Sign Language]]}}
{{Legend|#ff9691|[[Chinese Sign Language]]}}
{{Legend|#bd4b31|[[Japanese Sign Language family]]}}
{{Legend|#4b874b|[[BANZSL]] family (British, Australian and New Zealand Sign Language)}}
{{Legend|#1c5e31|[[South African Sign Language]] (within the BANZSL family)}}
{{Legend|#fff200|Isolated languages}}
{{Legend|#e6e6e6|No data}}]]Sign languages may be classified by how they arise.

In non-signing communities, [[home sign]] is not a full language, but closer to a [[pidgin]]. Home sign is amorphous and generally idiosyncratic to a particular family, where a deaf child does not have contact with other deaf children and is not educated in sign. Such systems are not generally passed on from one generation to the next. Where they are passed on, [[creole genesis|creolization]] would be expected to occur, resulting in a full language.  However, home sign may also be closer to full language in communities where the hearing population has a gestural mode of language; examples include various [[Australian Aboriginal sign languages]] and gestural systems across West Africa, such as [[Mofu-Gudur Sign Language|Mofu-Gudur]] in Cameroon.

A [[village sign language]] is a local indigenous language that typically arises over several generations in a relatively insular community with a high incidence of deafness, and is used both by the deaf and by a significant portion of the hearing community, who have deaf family and friends.<ref>{{cite book |last1= Meir |first1= Irit |last2= Sandler |first2= Wendy |last3= Padden |first3= Carol |author-link3= Carol Padden |last4= Aronoff |first4= Mark |author-link4= Mark Aronoff |year= 2010 |chapter= Chapter 18: Emerging sign languages |chapter-url= http://sandlersignlab.haifa.ac.il/html/html_eng/pdf/EMERGING_SIGN_LANGUAGES.pdf |editor1-last= Marschark |editor1-first= Marc |editor2-last= Spencer |editor2-first= Patricia Elizabeth |title= Oxford Handbook of Deaf Studies, Language, and Education |url= https://books.google.com/books?id=0mmJAgAAQBAJ |volume= 2 |location= New York |publisher= [[Oxford University Press]] |isbn= 978-0-19-539003-2 |oclc= 779907637 |access-date= 2016-11-05 |archive-date= 2023-01-14 |archive-url= https://web.archive.org/web/20230114125751/https://books.google.com/books?id=0mmJAgAAQBAJ |url-status= live }}</ref> The most famous of these is probably the extinct [[Martha's Vineyard Sign Language]] of the U.S., but there are also numerous village languages scattered throughout Africa, Asia, and America.

[[Deaf-community sign language]]s, on the other hand, arise where deaf people come together to form their own communities. These include school sign, such as [[Nicaraguan Sign Language]], which develop in the student bodies of deaf schools which do not use sign as a language of instruction, as well as community languages such as [[Bamako Sign Language]], which arise where generally uneducated deaf people congregate in urban centers for employment. At first, Deaf-community sign languages are not generally known by the hearing population, in many cases not even by close family members. However, they may grow, in some cases becoming a language of instruction and receiving official recognition, as in the case of ASL.

Both contrast with [[speech taboo|speech-taboo]] languages such as the various [[Aboriginal Australian sign languages]], which are developed by the hearing community and only used secondarily by the deaf. It is doubtful whether most of these are languages in their own right, rather than manual codes of spoken languages, though a few such as [[Yolngu Sign Language]] are independent of any particular spoken language. Hearing people may also develop sign to communicate with users of other languages, as in [[Plains Indian Sign Language]]; this was a contact signing system or [[pidgin]] that was evidently not used by deaf people in the Plains nations, though it presumably influenced home sign.

[[Language contact]] and creolization is common in the development of sign languages, making clear family classifications difficult– it is often unclear whether lexical similarity is due to borrowing or a common parent language, or whether there was one or several parent languages, such as several village languages merging into a Deaf-community language. Contact occurs between sign languages, between sign and spoken languages ([[contact sign]], a kind of pidgin), and between sign languages and [[gesture|gestural systems]] used by the broader community. For example, [[Adamorobe Sign Language]], a village sign language of Ghana, may be related to the "gestural trade jargon used in the markets throughout West Africa", in vocabulary and [[areal feature]]s including prosody and phonetics.<ref>Frishberg, Nancy (1987). "Ghanaian Sign Language." In: Cleve, J. Van (ed.), ''Gallaudet encyclopaedia of deaf people and deafness''. New York: McGraw-Hill Book Company. {{ISBN|9780070792296}}</ref><ref name="Wittmann, H. 1991">Wittmann, H. (1991). Classification linguistique des langues signées non vocalement. ''Revue québécoise de linguistique théorique et appliquée'', 10(1), 88.</ref>

[[File:Lao sign language 025.jpg|thumb|Young students learn some words of [[Lao sign language]] from Suliphone, a deaf artist. This was one of several activities at a school book party sponsored by Big Brother Mouse, a literacy project in [[Laos]] where Suliphone works.]]
* [[British Sign Language|BSL]], [[Auslan]] and [[NZSL]] are usually considered to be a language known as [[BANZSL]]. [[Maritime Sign Language]] and [[South African Sign Language]] are also related to BSL.<ref>See Gordon (2008), under nsr {{cite web |url=http://www.ethnologue.com/show_language.asp?code=nsr |title=Maritime Sign Language |access-date=2011-06-01 |url-status=live |archive-url=https://web.archive.org/web/20110604014547/http://www.ethnologue.com/show_language.asp?code=nsr |archive-date=2011-06-04 }} and sfs {{cite web |url=http://www.ethnologue.com/show_language.asp?code=sfs |title=South African Sign Language |access-date=2008-09-19 |url-status=live |archive-url=https://web.archive.org/web/20080921104537/http://www.ethnologue.com/show_language.asp?code=sfs |archive-date=2008-09-21 }}.</ref>
* [[Danish Sign Language]] and its descendants [[Norwegian Sign Language]] and [[Icelandic Sign Language]] are largely mutually intelligible with [[Swedish Sign Language]]. [[Finnish Sign Language]] and [[Portuguese Sign Language]] derive from Swedish SL, though with local admixture in the case of mutually unintelligible Finnish SL.{{clarify|date=September 2014}} Danish SL has French SL influence and Wittmann (1991) places them in that family,<ref name="Wittmann, H. 1991"/> though he proposes that Swedish, Finnish, and Portuguese SL are instead related to [[British Sign Language]].
* [[Swedish Sign Language family|Swedish Sign Language Family]] includes the following languages: [[Swedish Sign Language]], [[Finnish Sign Language]], [[Finland-Swedish Sign Language]], [[Portuguese Sign Language]], [[Eritrean Sign Language]] and the [[Cape Verdian Sign Language]],<ref>{{Cite web |title=State of Eritrea |url=https://africansignlanguagesresourcecenter.com/eritrea/ |access-date=2024-05-13 |website=African Sign Languages Resource Center |language=en-US |archive-date=2024-05-13 |archive-url=https://web.archive.org/web/20240513205208/https://africansignlanguagesresourcecenter.com/eritrea/ |url-status=live }}</ref><ref>{{Cite book |last=Jepsen |first=Julie |title=Sign Languages of the World: a Comparative Handbook |publisher=De Gruyter |year=2015}}</ref><ref name=":0">{{Cite web |title=Cape Verde |url=https://africansignlanguagesresourcecenter.com/cape-verde/ |access-date=2024-05-13 |website=African Sign Languages Resource Center |language=en-US |archive-date=2024-05-13 |archive-url=https://web.archive.org/web/20240513193111/https://africansignlanguagesresourcecenter.com/cape-verde/ |url-status=live }}</ref><ref>{{Cite web |last=Pinto |first=Mariana Correia |date=2017-11-14 |title=O que todos devíamos saber sobre língua gestual (em dez pontos) |url=https://www.publico.pt/2017/11/14/p3/noticia/o-que-todos-deviamos-saber-sobre-lingua-gestual-em-dez-pontos-1828846 |access-date=2024-05-13 |website=PÚBLICO |language=pt |archive-date=2024-05-13 |archive-url=https://web.archive.org/web/20240513195919/https://www.publico.pt/2017/11/14/p3/noticia/o-que-todos-deviamos-saber-sobre-lingua-gestual-em-dez-pontos-1828846 |url-status=live }}</ref> although some reports also say that the [[São Tomé and Príncipe Sign Language]] is largely intelligible with Portuguese Sign.<ref name=":02">{{Cite web |title=Democratic Republic of São Tomé and Príncipe |url=https://africansignlanguagesresourcecenter.com/sao-tome-and-principe/ |access-date=2024-05-13 |website=African Sign Languages Resource Center |language=en-US |archive-date=2024-05-13 |archive-url=https://web.archive.org/web/20240513201434/https://africansignlanguagesresourcecenter.com/sao-tome-and-principe/ |url-status=live }}</ref>
* [[Indian Sign Language]] (ISL) is similar to [[Pakistani Sign Language]].
* [[Japanese Sign Language]], [[Taiwanese Sign Language]] and [[Korean Sign Language]] are thought to be members of a [[Japanese Sign Language family]].<ref>Fischer, Susan D. ''et al.'' (2010). "Variation in East Asian Sign Language Structures" in {{Google books|xI0uqGyrsN8C|''Sign Languages,''|page=499}}</ref>
* [[French Sign Language family]]. There are a number of sign languages that emerged from [[French Sign Language]] (LSF), or are the result of language contact between local community sign languages and LSF. These include: [[French Sign Language]], [[Italian Sign Language]], [[Quebec Sign Language]], [[American Sign Language]], [[Irish Sign Language]], [[Russian Sign Language]], [[Dutch Sign Language]] (NGT), [[Spanish Sign Language]], [[Mexican Sign Language]], [[Brazilian Sign Language|Brazilian Sign Language (LIBRAS)]], [[Catalan Sign Language]], [[Ukrainian Sign Language]], [[Austrian Sign Language]] (along with its twin [[Hungarian Sign Language]] and its offspring [[Czech Sign Language]]) and others.
** A subset of this group includes languages that have been heavily influenced by American Sign Language (ASL), or are regional varieties of ASL. [[Bolivian Sign Language]] is sometimes considered a dialect of ASL. [[Thai Sign Language]] is a [[mixed language]] derived from ASL and the native sign languages of Bangkok and Chiang Mai, and may be considered part of the ASL family. Others possibly influenced by ASL include [[Ugandan Sign Language]], [[Kenyan Sign Language]], [[Philippine Sign Language]] and [[Malaysian Sign Language]].
** According to an SIL report,<ref>{{Cite web|date=2012-01-14|title=SIL Electronic Survey Reports: The signed languages of Eastern Europe|url=http://www.sil.org/silesr/abstract.asp?ref=2005-026|url-status=live|access-date=2021-08-23|archive-url=https://web.archive.org/web/20120114060622/http://www.sil.org/silesr/abstract.asp?ref=2005-026|archive-date=2012-01-14}}</ref> the sign languages of Russia, Moldova and Ukraine share a high degree of lexical similarity and may be dialects of one language, or distinct related languages. The same report suggested a "cluster" of sign languages centered around [[Czech Sign Language]], [[Hungarian Sign Language]] and [[Slovak Sign Language]]. This group may also include [[Romanian Sign Language|Romanian]], [[Bulgarian Sign Language|Bulgarian]], and [[Polish Sign Language|Polish]] sign languages.
* [[German Sign Language]] (DGS) gave rise to [[Polish Sign Language]]; it also at least strongly influenced [[Israeli Sign Language]], though it is unclear whether the latter derives from DGS or from [[Austrian Sign Language]], which is in the French family.
* The southern dialect of [[Chinese Sign Language]] gave rise to [[Hong Kong Sign Language]], used in Hong Kong and Macau
* [[Lyons Sign Language]] may be the source of [[Flemish Sign Language]] (VGT) though this is unclear.
* Sign languages of [[Jordanian Sign Language|Jordan]], Lebanon, Syria, Palestine, and Iraq (and possibly [[Saudi Sign Language|Saudi Arabia]]) may be part of a [[sprachbund]], or may be one dialect of a larger [[Eastern Arabic Sign Language]].
* Known [[Language isolate#Sign language isolates|isolates]] include [[Nicaraguan Sign Language]], [[Turkish Sign Language]], [[Armenian Sign Language]], [[Kata Kolok]], [[Al-Sayyid Bedouin Sign Language]] and [[Providence Island Sign Language]].

The only comprehensive classification along these lines going beyond a simple listing of languages dates back to 1991.<ref>Henri Wittmann (1991). The classification is said to be typological satisfying Jakobson's condition of genetic interpretability.</ref> The classification is based on the 69 sign languages from the 1988 edition of [[Ethnologue]] that were known at the time of the 1989 conference on sign languages in Montreal and 11 more languages the author added after the conference.{{refn |Wittmann's classification went into Ethnologue's database where it is still cited.<ref>{{cite web |editor1=Simons, Gary F. |editor2=Charles D. Fennig |year=2018 |title=Bibliography of Ethnologue Data Sources |work=Ethnologue: Languages of the World |edition=21st |publisher=SIL International |url=http://www.ethnologue.com/ethno_docs/bibliography.asp |access-date=2008-09-19 |url-status=live |archive-url=https://web.archive.org/web/20080725072840/http://www.ethnologue.com/ethno_docs/bibliography.asp |archive-date=2008-07-25 }}</ref> The subsequent edition of Ethnologue in 1992 went up to 81 sign languages, ultimately adopting Wittmann's distinction between primary and alternate sign languages (going back ultimately to Stokoe 1974) and, more vaguely, some other traits from his analysis. The 2013 version (17th edition) of [[Ethnologue]] is now up to 137 sign languages.}}

{| class = "wikitable"
|+ Wittmann classification of sign languages
!
! Primary<br />language
! Primary<br />group
! Auxiliary<br />language
! Auxiliary<br />group
|-
| Prototype-A<ref name=pro-A/>
|5<!--not 7: the other two are Chinese and Egyptian logograms, not sign languages at all-->
|1
|7
|2
|-
| Prototype-R<ref name=pro-R/>
|18
|1
|1
|–
|-
| [[BANZSL|BSL-derived]]
|8
|–
|–
|–
|-
| [[German Sign Language family|DGS-derived]]
|1 or 2
|–
|–
|–
|-
| [[Japanese Sign Language family|JSL-derived]]
|2
|
–
|–
|–
|-
| [[French Sign Language family|LSF-derived]]
|30
|–
|–
|–
|-
| [[Lyons Sign Language|LSG]]-derived
|
[[Flemish Sign Language|1?]]
|–
|–
|–
|}

In his classification, the author distinguishes between primary and auxiliary sign languages<ref>Wittmann adds that this taxonomic criterion is not really applicable with any scientific rigor: Auxiliary sign languages, to the extent that they are full-fledged natural languages (and therefore included in his survey) at all, are mostly used by the deaf as well, and some primary sign languages (such as ASL and [[Adamorobe Sign Language]]) have acquired auxiliary usages.</ref> as well as between single languages and names that are thought to refer to more than one language.<ref>Wittmann includes in this class [[Australian Aboriginal sign languages]] (at least 14 different languages), [[Monastic sign language]], Thai Hill-Country sign languages (possibly including languages in Vietnam and Laos), and [[Sri Lankan sign languages]] (14 deaf schools with different sign languages).</ref> The prototype-A class of languages includes all those sign languages that seemingly cannot be derived from any other language.<ref name="pro-A">These are [[Adamorobe Sign Language]], [[Armenian Sign Language]], [[Australian Aboriginal sign languages]], Hindu [[mudra]], the [[Monastic sign languages]], [[Martha's Vineyard Sign Language]], [[Plains Indian Sign Language]], [[Urubú-Kaapor Sign Language]], [[Chinese Sign Language]], [[Indo-Pakistani Sign Language]] (Pakistani SL is said to be R, but Indian SL to be A, though they are the same language), [[Japanese Sign Language]], and maybe the various [[Thai Hill-Country sign languages]], [[French Sign Language]], [[Lyons Sign Language]], and [[Mayan sign languages|Nohya Maya Sign Language]]. Wittmann also includes, bizarrely, Chinese characters and Egyptian hieroglyphs.</ref> Prototype-R languages are languages that are remotely modelled on a prototype-A language (in many cases thought to have been French Sign Language) by a process Kroeber (1940) called "[[stimulus diffusion]]".<ref name=pro-R>These are [[Providencia Island Sign Language|Providencia Island]], [[Kod Tangan Bahasa Malaysia]] (manually signed Malay), [[German Sign Language|German]], [[Ecuadorian Sign Language|Ecuadoran]], [[Salvadoran Sign Language|Salvadoran]], [[Gestuno]], [[Indo-Pakistani Sign Language|Indo-Pakistani]] (Pakistani SL is said to be R, but Indian SL to be A, though they are the same language), [[Kenyan Sign Language|Kenyan]], [[Brazilian Sign Language|Brazilian]], [[Spanish Sign Language|Spanish]], [[Nepali Sign Language|Nepali]] (with possible admixture), [[Penang Sign Language|Penang]], [[Rennellese Sign Language|Rennellese]], [[Saudi Sign Language|Saudi]], the various [[Sri Lankan sign languages]], and perhaps BSL, [[Peruvian Sign Language|Peruvian]], [[Tijuana Sign Language|Tijuana]] (spurious), [[Venezuelan Sign Language|Venezuelan]], and [[Nicaraguan Sign Language|Nicaraguan]] sign languages.</ref> The families of [[BANZSL|BSL]], [[German Sign Language|DGS]], [[Japanese Sign Language|JSL]], [[French Sign Language|LSF]] (and possibly [[Lyons Sign Language|LSG]]) were the products of [[creolization]] and [[relexification]] of prototype languages.<ref>Wittmann's references on the subject, besides his own work on [[creolization]] and [[relexification]] in spoken languages, include papers such as Fischer (1974, 1978), Deuchar (1987) and Judy Kegl's pre-1991 work on creolization in sign languages.</ref> Creolization is seen as enriching overt morphology in sign languages, as compared to reducing overt morphology in spoken languages.<ref>Wittmann's explanation for this is that models of acquisition and transmission for sign languages are not based on any typical parent-child relation model of direct transmission which is inducive to variation and change to a greater extent. He notes that sign creoles are much more common than vocal creoles and that we can't know on how many successive creolizations prototype-A sign languages are based prior to their historicity.{{Clarify|date=February 2011}}</ref>

=== Typology ===
{{See also|Linguistic typology}}

Linguistic typology (going back to [[Edward Sapir]]) is based on word structure and distinguishes [[Morphology (linguistics)|morphological]] classes such as [[Agglutination|agglutinating]]/concatenating, [[Inflexion|inflectional]], polysynthetic, incorporating, and isolating ones.

Sign languages vary in word-order typology. For example, Austrian Sign Language, Japanese Sign Language and [[Indo-Pakistani Sign Language]] are [[Subject-object-verb]] while ASL is [[Subject-verb-object]]. Influence from the surrounding spoken languages is not improbable.

Sign languages tend to be incorporating classifier languages, where a classifier handshape representing the object is incorporated into those transitive verbs which allow such modification. For a similar group of intransitive verbs (especially motion verbs), it is the subject which is incorporated. Only in a very few sign languages (for instance Japanese Sign Language) are agents ever incorporated. In this way, since subjects of intransitives are treated similarly to objects of transitives, incorporation in sign languages can be said to follow an ergative pattern.

Brentari<ref name="Brentari1998">Brentari, Diane (1998) ''A prosodic model of sign language phonology''. Cambridge, Massachusetts: MIT Press</ref><ref>{{cite book |last1=Brentari |first1=Diane |title=Modality and Structure in Signed and Spoken Languages |isbn=9780511486777 |chapter=Modality differences in sign language phonology and morphophonemics |year=2002 |pages=35–36 |doi=10.1017/CBO9780511486777.003 |editor1=P. Meier |editor2=Kearsy Cormier |editor3=David Quinto-Pozos}}</ref> classifies sign languages as a whole group determined by the medium of communication (visual instead of auditory) as one group with the features monosyllabic and polymorphemic. That means, that one syllable (i.e. one word, one sign) can express several morphemes, e.g., subject and object of a verb determine the direction of the verb's movement (inflection).

Another aspect of typology that has been studied in sign languages is their systems for [[Cardinal number (linguistics)|cardinal numbers]].<ref>{{cite journal|last1=Ulrike|first1=Zeshan|last2=Escobedo Delgado|first2=Cesar Ernesto|last3=Dikyuva|first3=Hasan|last4=Panda|first4=Sibaji|last5=de Vos|first5=Connie|title=Cardinal numerals in rural sign languages: Approaching cross-modal typology|journal=Linguistic Typology|volume=17|issue=3|year=2013|url=https://www.researchgate.net/publication/261473038|doi=10.1515/lity-2013-0019|hdl=11858/00-001M-0000-0013-B2E1-B|s2cid=145616039|hdl-access=free}}</ref> Typologically significant differences have been found between sign languages.

=== Acquisition ===
{{See also|Language acquisition}}

Children who are exposed to a sign language from birth will acquire it, just as hearing children acquire their native spoken language.<ref>{{cite book|last=Emmorey|first=Karen|title=Language, Cognition, and the Brain|year=2002|publisher=Lawrence Erlbaum Associates|location=Mahwah, NJ}}</ref> In a study done at the University of McGill, they found that American Sign Language users who acquired the language natively (from birth) performed better when asked to copy videos of ASL sentences than ASL users who acquired the language later in life. They also found that there are differences in the grammatical morphology of ASL sentences between the two groups, all suggesting that there is a very important critical period in learning signed languages.<ref>{{Cite web|url=http://www.acfos.org/publication/ourarticles/pdf/acfos1/mayberry.pdf|title=The Critical Period for Language Acquisition and The Deaf Child's Language Comprehension: A Psycholinguistic Approach|last=Mayberry|first=Rachel|website=ACFOS|url-status=live|archive-url=https://web.archive.org/web/20171201072124/http://www.acfos.org/publication/ourarticles/pdf/acfos1/mayberry.pdf|archive-date=2017-12-01}}</ref>

The acquisition of non-manual features follows an interesting pattern: When a word that always has a particular non-manual feature associated with it (such as a [[Wh question|wh-question]] word) is learned, the non-manual aspects are attached to the word but do not have the flexibility associated with adult use. At a certain point, the non-manual features are dropped and the word is produced with no facial expression. After a few months, the non-manuals reappear, this time being used the way adult signers would use them.<ref>{{cite book|title=Advances in the Sign Language Development of Deaf Children|year=2005|publisher=Oxford University Press|location=Cary, NC|isbn=978-0-19-803996-9|pages=262–290|author=Reilly, Judy|editor1=Brenda Schick |editor2=Marc Marschack |editor3=Patricia Elizabeth Spencer |chapter=How Faces Come to Serve Grammar: The Development of Nonmanual Morphology in American Sign Language}}</ref>

=== Written forms ===
{{anchor|Notation}}<!-- [[Sign language notation]] redirects here -->
Sign languages do not have a traditional or formal written form. Many deaf people do not see a need to write their own language.<ref>{{cite journal | last1 = Hopkins | first1 = Jason | year = 2008 | title = Choosing how to write sign language: a sociolinguistic perspective | journal = [[International Journal of the Sociology of Language]] | volume = 2008 | issue = 192| pages = 75–90 | doi=10.1515/ijsl.2008.036| s2cid = 145429638 }}</ref>

Several ways to represent sign languages in written form have been developed.

* [[Stokoe notation]], devised by Dr. [[William Stokoe]] for his 1965 ''Dictionary of American Sign Language'',<ref name="StokoeWilliam">[[William Stokoe|Stokoe, William C.]]; [[Dorothy C. Casterline]]; [[Carl G. Croneberg]]. 1965. ''A dictionary of American sign language on linguistic principles''. Washington, D.C.: Gallaudet College Press</ref> is an abstract [[phonemic]] notation system. Designed specifically for representing the use of the hands, it has no way of expressing facial expression or other non-manual features of sign languages. However, his was designed for research, particularly in a dictionary, not for general use.
* The [[Hamburg Notation System]] (HamNoSys), developed in the early 1990s, is a detailed phonetic system, not designed for any one sign language, and intended as a transcription system for researchers rather than as a practical script.
* [[David J. Peterson]] has attempted to create a phonetic transcription system for signing that is [[ASCII]]-friendly known as the [https://dedalvs.com/slipa.html Sign Language International Phonetic Alphabet (SLIPA)].
* [[SignWriting]], developed by Valerie Sutton in 1974, is a system for representing sign languages phonetically (including [[mouthing]], facial expression and dynamics of movement). The script is sometimes used for detailed research, language documentation, as well as publishing texts and works in sign languages.
* [[si5s]] is another orthography which is largely phonemic. However, a few signs are [[logogram|logographs]] and/or [[ideograph]]s due to regional variation in sign languages.
* [[ASL-phabet]] is a system designed primarily for education of deaf children by Dr. [[Samuel James Supalla|Sam Supalla]] which uses a minimalist collection of symbols in the order of Handshape-Location-Movement. Many signs can be written the same way ([[homograph]]).
*The Alphabetic Writing System for sign languages ({{Lang|es|Sistema de escritura alfabética}}, SEA, by its Spanish name and acronym), developed by linguist Ángel Herrero Blanco and two deaf researchers, Juan José Alfaro and Inmacualada Cascales, was published as a book in 2003<ref>{{Cite book|title=Escritura alfabética de la Lengua de Signos Española : once lecciones|last=Herrero Blanco, Ángel L.|date=2003|publisher=Publicaciones de la Universidad de Alicante|others=Alfaro, Juan José,, Cascales, Inmaculada|isbn=9781282574960|location=San Vicente del Raspeig [Alicante]|oclc=643124997}}</ref> and made accessible in [[Spanish Sign Language]] on-line.<ref>{{Cite web|url=http://www.cervantesvirtual.com/seccion/signos/psegundonivel.jsp?seccion=signos&conten=materiales&pagina=cat_materiales1&tit3=Lecciones+de+escritura+alfab%25E9tica+de+LSE|title=Biblioteca de signos – Materiales|website=www.cervantesvirtual.com|access-date=2019-07-07|archive-date=2020-09-06|archive-url=https://web.archive.org/web/20200906213725/http://www.cervantesvirtual.com/seccion/signos/psegundonivel.jsp?seccion=signos&conten=materiales&pagina=cat_materiales1&tit3=Lecciones+de+escritura+alfab%E9tica+de+LSE|url-status=dead}}</ref> This system makes use of the letters of the Latin alphabet with a few diacritics to represent sign through the morphemic sequence S L C Q D F (bimanual sign, place, contact, handshape, direction and internal form). The resulting words are meant to be read by signing. The system is designed to be applicable to any sign language with minimal modification and to be usable through any medium without special equipment or software. Non-manual elements can be encoded to some extent, but the authors argue that the system does not need to represent all elements of a sign to be practical, the same way written oral language does not. The system has seen some updates which are kept publicly on a wiki page.<ref>{{Cite web|url=http://wiki.apertium.org/wiki/Traductor_de_espa%C3%B1ol_a_LSE|title=Traductor de español a LSE – Apertium|website=wiki.apertium.org|access-date=2019-07-07|archive-date=2019-07-03|archive-url=https://web.archive.org/web/20190703071935/http://wiki.apertium.org/wiki/Traductor_de_espa%C3%B1ol_a_LSE|url-status=live}}</ref> The Center for Linguistic Normalization of Spanish Sign Language has made use of SEA to transcribe all signs on its dictionary.<ref>{{Cite web|url=http://sid.usal.es/libros/discapacidad/20740/8-7-2/diccionario-normativo-de-la-lengua-de-signos-espanola-dvd.aspx|title=Diccionario normativo de la lengua de signos española ... (SID)|website=sid.usal.es|language=es|access-date=2019-07-07|archive-date=2019-07-07|archive-url=https://web.archive.org/web/20190707142030/http://sid.usal.es/libros/discapacidad/20740/8-7-2/diccionario-normativo-de-la-lengua-de-signos-espanola-dvd.aspx|url-status=dead}}</ref>

So far, there is no consensus regarding the written form of sign language.  Except for SignWriting, none are widely used. Maria Galea writes that SignWriting "is becoming widespread, uncontainable and untraceable. In the same way that works written in and about a well developed writing system such as the Latin script, the time has arrived where SW is so widespread, that it is impossible in the same way to list all works that have been produced using this writing system and that have been written about this writing system."<ref name="GaleaLinguistic">{{cite book
 |last        = Galea
 |first       = Maria
 |title       = SignWriting (SW) of Maltese Sign Language (LSM) and its development into an orthography: Linguistic considerations
 |year        = 2014
 |type        = Ph.D. dissertation
 |publisher   = University of Malta
 |location    = Malta
 |url         = https://www.academia.edu/10451785
 |access-date  = 4 February 2015
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20180513202709/http://www.academia.edu/10451785/SignWriting_SW_of_Maltese_Sign_Language_LSM_and_its_development_into_an_orthography_Linguistic_considerations
 |archive-date = 13 May 2018
}}</ref>  In 2015, the [[Federal University of Santa Catarina]] accepted a dissertation written in Brazilian Sign Language using Sutton SignWriting for a master's degree in linguistics.  The dissertation "The Writing of Grammatical Non-Manual Expressions in Sentences in LIBRAS Using the SignWriting System" by João Paulo Ampessan states that "the data indicate the need for [non-manual expressions] usage in writing sign language".<ref>Ampessan, João Paulo. "The Writing of Grammatical Non-Manual Expressions in Sentences in LIBRAS Using the SignWriting System." ''Universidade Federal de Santa Catarina'', 2015. [https://web.archive.org/web/20210129185100/https://repositorio.ufsc.br/bitstream/handle/123456789/180688/351070.pdf Archived] from [https://repositorio.ufsc.br/bitstream/handle/123456789/180688/351070.pdf the original] on 29 January 2021.</ref>

=== Sign perception ===
For a native signer, sign [[Categorical perception|perception]] influences how the mind makes sense of their visual language experience. For example, a handshape may vary based on the other signs made before or after it, but these variations are arranged in perceptual categories during its development.  The mind detects handshape contrasts but groups similar handshapes together in one category.<ref>{{cite journal |author1=Morford, Jill P. |author2=Staley, Joshua |author3=Burns, Brian |date=Fall 2010 |url=http://dsdj.gallaudet.edu/assets/section/section2/entry94/DSDJ_entry94.pdf |title=Seeing Signs: Language Experience and Handshape Perception |others=Videography by Jo Santiago and Brian Burns |journal=Deaf Studies Digital Journal |issue=2 |access-date=2011-12-14 |url-status=live |archive-url=https://web.archive.org/web/20120111142013/http://dsdj.gallaudet.edu/assets/section/section2/entry94/DSDJ_entry94.pdf |archive-date=2012-01-11 }}</ref><ref>{{cite journal | last1 = Kuhl | first1 = P | year = 1991 | title = Human adults and human infants show a 'perceptual magnet effect' for the prototypes of speech categories, monkeys do not | journal = Perception and Psychophysics | volume = 50 | issue = 2| pages = 93–107 | doi=10.3758/bf03212211| pmid = 1945741 | doi-access = free }}</ref><ref>{{cite journal | last1 = Morford | first1 = J. P. | last2 = Grieve-Smith | first2 = A. B. | last3 = MacFarlane | first3 = J. | last4 = Staley | first4 = J. | last5 = Waters | first5 = G. S. | year = 2008| title = Effects of language experience on the perception of American Sign Language | journal = Cognition | volume = 109 | issue = 41–53| pages = 41–53 | doi=10.1016/j.cognition.2008.07.016| pmid = 18834975 | pmc = 2639215 }}</ref> Different handshapes are stored in other categories.  The mind ignores some of the similarities between different perceptual categories, at the same time preserving the visual information within each perceptual category of handshape variation.

== In society ==

=== Deaf communities and Deaf culture ===
{{Main|Deaf culture}}

When Deaf people constitute a relatively small proportion of the general population, Deaf communities often develop that are distinct from the surrounding hearing community.<ref name="WollLadd2003">{{citation
|last1 = Woll
|first1 = Bencie
|last2 = Ladd
|first2 = Paddy
|date = 2003
|chapter = Deaf communities
|editor-last1 = Marschark
|editor-first1 = Marc
|editor-last2 = Spencer
|editor-first2 = Patricia Elizabeth
|title = Oxford handbook of deaf studies, language, and education
|place = Oxford UK
|publisher = Oxford University Press
|isbn = 978-0-195-14997-5
}}</ref>
These Deaf communities are very widespread in the world, associated especially with sign languages used in urban areas and throughout a nation, and the cultures they have developed are very rich.

One example of sign language variation in the Deaf community is [[Black ASL]]. This sign language was developed in the Black Deaf community as a variant during the American era of segregation and racism, where young Black Deaf students were forced to attend separate schools than their white Deaf peers.<ref>McCaskill, C. (2011). The hidden treasure of Black ASL: its history and structure. Washington, D.C.: Gallaudet University Press.</ref>

=== Use of sign languages in hearing communities ===
On occasion, where the prevalence of deaf people is high enough, a deaf sign language has been taken up by an entire local community, forming what is sometimes called a "village sign language"<ref name="ZeshanDeVos2012">{{cite book
|last1 = Zeshan
|first1 = Ulrike
|last2 = de Vos
|first2 = Connie
|date = 2012
|title = Sign languages in village communities: Anthropological and linguistic insights
|publisher = De Gruyter Mouton and Ishara Press
|place = Berlin and Nijmegen
}}</ref> or "shared signing community".<ref name="Kisch2008">{{cite journal
|last = Kisch
|first = Shifra
|date = 2008
|title = "Deaf discourse": The social construction of deafness in a Bedouin community
|journal = Medical Anthropology
|volume = 27
|issue = 3
|pages = 283–313
|doi = 10.1080/01459740802222807
|pmid = 18663641
|hdl = 11245/1.345005
|s2cid = 1745792
|url = http://dare.uva.nl/personal/pure/en/publications/deaf-discourse-the-social-construction-of-deafness-in-a-bedouin-community(eb0cb2ac-7045-40fe-8bcf-a40b2c534003).html
|access-date = 2018-12-20
|archive-date = 2024-05-26
|archive-url = https://web.archive.org/web/20240526073548/https://dare.uva.nl/search?identifier=eb0cb2ac-7045-40fe-8bcf-a40b2c534003
|url-status = live
}}</ref> Typically this happens in small, tightly integrated communities with a closed gene pool. Famous examples include:
* [[Martha's Vineyard Sign Language]], [[United States]]
* [[Al-Sayyid Bedouin Sign Language]], [[Israel]]
* [[Kata Kolok]], [[Bali]]
* [[Adamorobe Sign Language]], [[Ghana]] 
* [[Mayan Sign Language#Yucatec Mayan Sign Language|Yucatec Maya Sign Language]], [[Mexico]] 
In such communities deaf people are generally well-integrated in the general community and not socially disadvantaged, so much so that it is difficult to speak of a separate "Deaf" community.<ref name="WollLadd2003" />

Many [[Australian Aboriginal sign languages]] arose in a context of extensive speech taboos, such as during mourning and initiation rites. They are or were especially highly developed among the [[Warlpiri Sign Language|Warlpiri]], [[Warumungu people|Warumungu]], [[Dieri]], [[Kaytetye people|Kaytetye]], [[Arrernte people|Arrernte]], and [[Warlmanpa language|Warlmanpa]], and are based on their respective spoken languages.

A sign language arose among tribes of [[Native Americans in the United States|American Indians]] in the [[Great Plains]] region of [[North America]] (see [[Plains Indian Sign Language]]) before European contact. It was used by hearing people to communicate among tribes with different spoken [[language]]s, as well as by deaf people. There are especially users today among the [[Crow tribe|Crow]], [[Cheyenne]], and [[Arapaho]].

Sign language is also used as a form of alternative or augmentative communication by people who can hear but have difficulties using their voices to speak.<ref>{{Cite web|url=https://napacenter.org/aac-autism|title=Benefits of Sign Language and Other Forms of AAC for Autism|date=3 June 2020|access-date=7 March 2022|archive-date=7 March 2022|archive-url=https://web.archive.org/web/20220307202110/https://napacenter.org/aac-autism/|url-status=live}}</ref>

Increasingly, hearing schools and universities are expressing interest in incorporating sign language. In the U.S., enrollment for ASL (American Sign Language) classes as part of students' choice of second language is on the rise.<ref>{{Cite web|last1=Looney|first1=Dennis|last2=Lusin|first2=Natalia|date=February 2018|title=Enrollments in Languages Other Than English in United States Institutions of Higher Education, Summer 2016 and Fall 2016: Preliminary Report|url=https://www.mla.org/content/download/83540/2197676/2016-Enrollments-Short-Report.pdf|url-status=live|archive-url=https://web.archive.org/web/20210816111722/https://www.mla.org/content/download/83540/2197676/2016-Enrollments-Short-Report.pdf|archive-date=2021-08-16|publisher=[[Modern Language Association]]}}</ref> In New Zealand, one year after the passing of NZSL Act 2006 in parliament, a NZSL curriculum was released for schools to take NZSL as an optional subject. The curriculum and teaching materials were designed to target intermediate schools from Years 7 to 10, ([https://www.nzherald.co.nz/nz/schools-to-put-sign-language-on-curriculum/7XXV6VUP2WMOD77LOS7E3H4IRY/ NZ Herald], 2007).

=== Legal recognition ===
{{Main|Legal recognition of sign languages}}
Some sign languages have obtained some form of legal recognition, while others have no status at all. Sarah Batterbury has argued that sign languages should be recognized and supported not merely as an accommodation for those with disabilities, but as the communication medium of language communities.<ref>Sarah C. E. Batterbury. 2012. ''Language Policy'' 11:253–272.</ref>

Legal requirements covering sign language accessibility in media vary from country to country. In the [[United Kingdom]], the [[Broadcasting Act 1996]] addressed the requirements for blind and deaf viewers,<ref>{{cite web |url=http://www.ofcom.org.uk/static/archive/itc/itc_publications/codes_guidance/sign_language_dtt/introduction.asp.html |title=ITC Guidelines on Standards for Sign Language on Digital Terrestrial Television |access-date=2008-01-30 |url-status=live |archive-url=https://web.archive.org/web/20070423180334/http://www.ofcom.org.uk/static/archive/itc/itc_publications/codes_guidance/sign_language_dtt/introduction.asp.html |archive-date=2007-04-23 }}</ref> but has since been replaced by the [[Communications Act 2003]].

=== Interpretation ===
{{Main|Language interpretation#Sign language}}
[[File:2017 Woodstock 022 Język migowy.jpg|thumb|A [[Polish Sign Language]] interpreter at the [[Przystanek Woodstock]] in 2017]]
In order to facilitate communication between deaf and hearing people, sign language interpreters are often used.  Such activities involve considerable effort on the part of the interpreter, since sign languages are distinct [[natural language]]s with their own [[syntax]], different from any spoken language.

The interpretation flow is normally between a sign language and a spoken language that are customarily used in the same country, such as [[French Sign Language]] (LSF) and spoken French in France, [[Spanish Sign Language]] (LSE) to spoken Spanish in Spain, [[British Sign Language]] (BSL) and spoken English in the U.K., and [[American Sign Language]] (ASL) and spoken English in the U.S. and most of anglophone Canada (since BSL and ASL are distinct sign languages both used in English-speaking countries), etc. Sign language interpreters who can translate between signed and spoken languages that are not normally paired (such as between LSE and English), are also available, albeit less frequently.

[[File:Red de museos para la atencion a personas con discapacidad.webm|thumb|Video about access to cultural institutions in Mexico, with Mexican sign language interpretation and captions in Spanish]]

Sign language is sometimes provided for [[television program]]mes that include speech. The signer usually appears in the bottom corner of the screen, with the programme being [[broadcasting|broadcast]] full size or slightly shrunk away from that corner. Typically for [[press conference]]s such as those given by the [[Mayor of New York City]], the signer appears to stage left or right of the public official to allow both the speaker and signer to be in frame at the same time. Live sign interpretation of important televised events is increasingly common but still an informal industry <ref>{{Cite web |last1=de Wit |first1=Maya |last2=Pérez |first2=Sheyla M. |last3=Peterson |first3=Paal Richard |title=Sign language interpreting on TV and media: sharing best practices |url=https://static1.squarespace.com/static/5241699de4b09847f93f8123/t/5fc407ad18e72e5fdb558e80/1606682553723/Sign+language+interpreting+on+TV+and+media-+sharing+best+practices+.pdf |access-date=23 September 2023 |website=static1.squarespace.com |archive-date=24 April 2023 |archive-url=https://web.archive.org/web/20230424220627/https://static1.squarespace.com/static/5241699de4b09847f93f8123/t/5fc407ad18e72e5fdb558e80/1606682553723/Sign+language+interpreting+on+TV+and+media-+sharing+best+practices+.pdf |url-status=live }}</ref> In traditional analogue broadcasting, some programmes are repeated outside main viewing hours with a signer present.<ref name="RNID">{{cite web |url=http://www.rnid.org.uk/howwehelp/research_and_technology/communication_and_broadcasting/signing_on_television/ |title=Sign Language on Television |access-date=2008-01-30 |publisher=RNID |url-status=dead |archive-url=https://web.archive.org/web/20090417003132/http://www.rnid.org.uk/howwehelp/research_and_technology/communication_and_broadcasting/signing_on_television |archive-date=2009-04-17 }}</ref> Some emerging [[television]] technologies allow the viewer to turn the signer on and off in a similar manner to [[subtitles]] and [[closed captioning]].<ref name="RNID"/>

=== Technology ===
[[File:Deaf or HoH person at his workplace using a Video Relay Service to communicate with a hearing person via a Video Interpreter and sign language SVCC 2007 Brigitte SLI + Mark.jpg|thumb|right|A deaf person using a remote VRS interpreter to communicate with a hearing person]]

One of the first demonstrations of the ability for [[telecommunications]] to help sign language users communicate with each other occurred when [[AT&T Corporation|AT&T]]'s [[videophone]] (trademarked as the Picturephone) was introduced to the public at the [[1964 New York World's Fair]]– two deaf users were able to freely communicate with each other between the fair and another city.<ref name="BellLabs">Bell Laboratories RECORD (1969) [http://www.porticus.org/bell/pdf/picturephone.pdf A collection of several articles on the AT&T Picturephone] {{webarchive|url=https://web.archive.org/web/20120623215926/http://www.porticus.org/bell/pdf/picturephone.pdf |date=2012-06-23 }} (then about to be released) Bell Laboratories, Pg.134–153 & 160–187, Volume 47, No. 5, May/June 1969;</ref> However, video communication did not become widely available until sufficient bandwidth for the high volume of video data became available in the early 2000s.

The Internet now allows deaf people to talk via a [[video link]], either with a special-purpose [[videophone]] designed for use with sign language or with "off-the-shelf" [[videotelephony|video services]] designed for use with broadband and an ordinary computer [[webcam]].  The [[List of video telecommunication services and product brands|special videophones]] that are designed for sign language communication may provide better quality than 'off-the-shelf' services and may use data compression methods specifically designed to maximize the intelligibility of sign languages. Some advanced equipment enables a person to remotely control the other person's video camera, in order to zoom in and out or to point the camera better to understand the signing.

<!-- Note: the following text was originally copied from [[Language interpretation#Video interpreting|Language interpretation]]
but has been adapted extensively to fit into the context of this article.
 -->
[[File:Video interpreter.svg|thumb|upright|Video interpreter sign used at VRS/VRI service locations]]
{{Main|Video remote interpreting|Video relay service}}

Interpreters may be physically present with both parties to the conversation but, since the technological advancements in the early 2000s, provision of interpreters in remote locations has become available.  In [[video remote interpreting]] (VRI), the two clients (a sign language user and a hearing person who wish to communicate with each other) are in one location, and the interpreter is in another. The interpreter communicates with the sign language user via a video telecommunications link, and with the hearing person by an audio link. VRI can be used for situations in which no on-site interpreters are available.

However, VRI cannot be used for situations in which all parties are speaking via telephone alone. With [[video relay service]] (VRS), the sign language user, the interpreter, and the hearing person are in three separate locations, thus allowing the two clients to talk to each other on the phone through the interpreter.

With recent developments in [[artificial intelligence]] in [[computer science]], some recent deep learning based [[machine translation of sign languages|machine translation algorithms]] have been developed which automatically translate short videos containing sign language directly to written language.<ref>{{cite conference |last1=Huang |first1=Jie |last2=Zhou |first2=Wengang |last3=Zhang |first3=Qilin |last4=Li |first4=Houqiang |last5=Li |first5=Weiping |title=Video-based Sign Language Recognition without Temporal Segmentation |conference=32nd AAAI Conference on Artificial Intelligence (AAAI-18), Feb. 2–7, 2018, New Orleans, Louisiana, US |date=2018-01-30 |url=https://qilin-zhang.github.io/_pages/pdfs/VideobasedSignLanguageRecognitionwithoutTemporalSegmentation.pdf |url-status=live |archive-url=https://web.archive.org/web/20180329054531/https://qilin-zhang.github.io/_pages/pdfs/VideobasedSignLanguageRecognitionwithoutTemporalSegmentation.pdf |archive-date=2018-03-29 |arxiv=1801.10111 }}</ref>

Sign language has been incorporated into [[film]]; for example, all movies shown in Brazilian movie theaters must have a [[Brazilian Sign Language]] video track available to play alongside the film via a [[second screen]].<ref>{{Cite web |date=18 Sep 2017 |title=Deluxe Launches First Brazilian Sign Language (LIBRAS) Localization Service Outside Brazil |url=https://www.prnewswire.com/news-releases/deluxe-launches-first-brazilian-sign-language-libras-localization-service-outside-brazil-300521137.html |access-date=14 Nov 2023 |website=Cision PR Newswire |publisher=Deluxe Entertainment Services Group Inc. through Cision PR Newswire |archive-date=14 November 2023 |archive-url=https://web.archive.org/web/20231114213722/https://www.prnewswire.com/news-releases/deluxe-launches-first-brazilian-sign-language-libras-localization-service-outside-brazil-300521137.html |url-status=live }}</ref><ref>{{Cite web |title=Accessibility & The Audio Track File |url=https://cinepedia.com/accessibility/accessibility-the-audio-track-file/ |access-date=14 November 2023 |website=Cinepedia |archive-date=14 November 2023 |archive-url=https://web.archive.org/web/20231114215528/https://cinepedia.com/accessibility/accessibility-the-audio-track-file/ |url-status=live }}</ref> {{clear}}

=== Sign Union flag ===
[[File:Sign Union flag.svg|thumb|The Sign Union flag|187x187px]]The Sign Union flag was designed by [[Arnaud Balard]]. After studying flags around the world and [[vexillology]] principles for two years, Balard revealed the design of the flag, featuring the stylized outline of a hand. The three colors which make up the flag design are representative of Deafhood and humanity (dark blue), sign language (turquoise), and enlightenment and hope (yellow). Balard intended the flag to be an international symbol which welcomes deaf people.<ref name="DeafArt2020">{{cite web |last1=Durr |first1=Patti |title=Arnaud Balard |url=https://deaf-art.org/profiles/arnaud-balard/ |website=Deaf Art |publisher=National Technical Institute for the Deaf |access-date=17 April 2022 |date=2020 |archive-date=17 April 2022 |archive-url=https://web.archive.org/web/20220417191152/https://deaf-art.org/profiles/arnaud-balard/ |url-status=live }}</ref>

=== Language endangerment and extinction ===
As with any spoken language, sign languages are also vulnerable to becoming [[Endangered languages|endangered]].<ref>Bickford, J. Albert, and Melanie McKay-Cody (2018). [https://www.sil.org/system/files/reapdata/12/96/81/129681979560727324424065691676610323327/SignLanguageRevitalizationChapter_author_preprint.pdf "Endangerment and revitalization of sign languages"] {{Webarchive|url=https://web.archive.org/web/20210831131013/https://www.sil.org/system/files/reapdata/12/96/81/129681979560727324424065691676610323327/SignLanguageRevitalizationChapter_author_preprint.pdf |date=2021-08-31 }}, pp. 255–264 in ''The Routledge handbook of language revitalization''.</ref> For example, a sign language used by a small community may be endangered and even abandoned as users [[Language shift|shift]] to a sign language used by a larger community, as has happened with [[Hawai'i Sign Language]], which is almost extinct except for a few elderly signers.<ref>{{Cite web|url=http://www.endangeredlanguages.com/lang/hps|title=Did you know Hawai'i Sign Language is critically endangered?|website=Endangered Languages|access-date=2016-02-28|url-status=live|archive-url=https://web.archive.org/web/20160307065744/http://www.endangeredlanguages.com/lang/hps|archive-date=2016-03-07}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=sl_dDVctycgC|title=International Encyclopedia of Linguistics|date=2003-01-01|publisher=Oxford University Press|isbn=9780195139778|language=en|quote=The language is considered to be endangered. 9,600 deaf people in Hawaii now use American Sign Language with a few local signs for place-names and cultural items.|access-date=2016-02-28|archive-date=2023-01-14|archive-url=https://web.archive.org/web/20230114125752/https://books.google.com/books?id=sl_dDVctycgC|url-status=live}}</ref> Even nationally recognised sign languages can be endangered; for example, New Zealand Sign Language is losing users.<ref>{{citation
 |last1        = McKee
 |first1       = Rachel
 |last2        = McKee
 |first2       = David
 |contribution = Assessing the vitality of NZSL
 |year         = 2016
 |title        = 12th International Conference on Theoretical Issues in Sign Language Research
 |place        = Melbourne, Australia
 |url          = http://www.victoria.ac.nz/lals/centres-and-institutes/dsru/McKee-Vitality-TISLR-2016-FINAL-edit-.pdf
 |url-status      = live
 |archive-url   = https://web.archive.org/web/20161101102128/http://www.victoria.ac.nz/lals/centres-and-institutes/dsru/McKee-Vitality-TISLR-2016-FINAL-edit-.pdf
 |archive-date  = 2016-11-01
}}</ref> Methods are being developed to assess the language vitality of sign languages.<ref>{{cite journal | last1 = Bickford | last2 = Albert | first2 = J. | last3 = Lewis | first3 = M. Paul | last4 = Simons | first4 = Gary F. | year = 2014 | title = Rating the vitality of sign languages | journal = Journal of Multilingual and Multicultural Development | volume = 36 | issue = 5| pages = 1–15 }}</ref>

{{col-float-begin|width=30em}}
;Endangered sign languages:
*[[Adamorobe Sign Language]] (AdaSL)<ref name="Velupillai">{{Cite book |last=Velupillai |first=Viveka |date=2012 |title=An Introduction to Linguistic Typology |url=https://books.google.com/books?id=WXQinkZvEVAC |location=Amsterdam, Philadelphia |publisher=John Benjamins Publishing |pages=57–58 |isbn=9789027211989 |access-date=16 April 2020 |archive-date=26 May 2024 |archive-url=https://web.archive.org/web/20240526073542/https://books.google.com/books?id=WXQinkZvEVAC |url-status=live }}</ref>
*[[Ban Khor Sign Language]] (BKSL)<ref name="Velupillai"/>
*[[Benkala Sign Language]] (KK)<ref name="Velupillai"/>
*[[Finland-Swedish Sign Language]] (FinSSL)<ref>{{Cite web|title=Sign languages in UNESCO's Atlas of the World's Languages in Danger Project|url=https://uclan.ac.uk/research/activity/atlas-of-world-languages-in-danger|access-date=2021-08-23|website=University of Central Lancashire|language=en|archive-date=2021-08-23|archive-url=https://web.archive.org/web/20210823105244/https://www.uclan.ac.uk/research/activity/atlas-of-world-languages-in-danger|url-status=live}}</ref>
*[[Hawai'i Sign Language]] (HPSL)<ref name="Velupillai"/>
*[[Inuit Sign Language]] (IUR)<ref name=Access>{{cite journal|last1=MacDougall|first1=Jamie|title=Access to justice for deaf Inuit in Nunavut: The role of "Inuit sign language"|journal=Canadian Psychology|date=February 2001|volume=41|issue=1|page=61|doi=10.1037/h0086880}}</ref>
*[[Jamaican Country Sign Language]] (KS)<ref>[[Ulrike Zeshan|Zeshan, Ulrike]]. (2007). ''The ethics of documenting sign languages in village communities.'' In Peter K. Austin, Oliver Bond & David Nathan (eds) [http://www.hrelp.org/publications/ldlt/papers/ldlt_31.pdf ''Proceedings of Conference on Language Documentation and Linguistic Theory.''] {{Webarchive|url=https://web.archive.org/web/20150924031540/http://www.hrelp.org/publications/ldlt/papers/ldlt_31.pdf |date=2015-09-24 }} London: SOAS. p. 271.</ref>
*[[Maritime Sign Language]] (MSL)<ref name="Velupillai"/>
*[[Old Bangkok Sign Language]] (OBSL)<ref name="Velupillai"/>
*[[Old Chiangmai Sign Language]] (OCSL)<ref name="Velupillai"/>
*[[Plains Indian Sign Language]] (PISL)<ref name="Velupillai"/>
*[[Providencia Sign Language]] (PSL)<ref name="Velupillai"/>
*[[Rennellese Sign Language]] (RSL)<ref name="Velupillai"/>
{{col-float-break|width=30em}}
;Extinct sign languages:
* [[Angami Naga Sign Language]]
* [[Henniker Sign Language]]
* [[Martha's Vineyard Sign Language]] (MVSL)
* [[Old French Sign Language]] (VLSF)
* [[Old Kentish Sign Language]] (OKSL)
* [[Pitta Pitta language#Sign|Pitta Pitta sign language]]
* [[Plateau Sign Language]]
* [[Sandy River Valley Sign Language]]
* [[Warluwarra language#Sign|Warluwarra sign language]]
{{col-float-end}}

== Communication systems similar to sign language ==
There are a number of communication systems that are similar in some respects to sign languages, while not having all the characteristics of a full sign language, particularly its grammatical structure. Many of these are either precursors to natural sign languages or are derived from them.

=== Manual codes for spoken languages ===
{{Main|Manually coded language}}

When Deaf and Hearing people interact, signing systems may be developed that use signs drawn from a natural sign language but used according to the grammar of the spoken language. In particular, when people devise one-for-one sign-for-word correspondences between spoken words (or even [[morphemes]]) and signs that represent them, the system that results is a manual code for a spoken language, rather than a natural sign language. Such systems may be invented in an attempt to help teach Deaf children the spoken language, and generally are not used outside an educational context.

=== "Baby sign language" with hearing children ===
{{Main|Baby sign language}}

Some hearing parents teach signs to young hearing children.  Since the muscles in babies' hands grow and develop quicker than their mouths, signs are seen as a beneficial option for better communication.<ref>Taylor-DiLeva, Kim. Once Upon A Sign : Using American Sign Language To Engage, Entertain, And Teach All Children, p. 15. Libraries Unlimited, 2011. eBook Collection (EBSCOhost). Web. 29 Feb. 2012.</ref> Babies can usually produce signs before they can speak.{{citation needed|date=February 2020}} This reduces the confusion between parents when trying to figure out what their child wants. When the child begins to speak, signing is usually abandoned, so the child does not progress to acquiring the grammar of the sign language.<ref>{{Cite web |date=2020-09-04 |title=Baby sign language: A helpful communication tool |url=https://www.canr.msu.edu/news/baby_sign_language_a_helpful_communication_tool |access-date=2024-06-30 |website=Child & Family Development |language=en-us}}</ref>

This is in contrast to hearing children who grow up with Deaf parents, who generally acquire the full sign language natively, the same as Deaf children of Deaf parents.

=== Home sign ===
{{Main|Home sign}}

Informal, rudimentary sign systems are sometimes developed within a single family. For instance, when hearing parents with no sign language skills have a deaf child, the child may develop a system of signs naturally, unless repressed by the parents. The term for these mini-languages is [[home sign]] (sometimes "kitchen sign").<ref>Susan Goldin-Meadow (Goldin-Meadow 2003, Van Deusen, Goldin-Meadow & Miller 2001) has done extensive work on home sign systems. [[Adam Kendon]] (1988) published a seminal study of the homesign system of a deaf [[Enga Province|Enga]] woman from the [[Papua New Guinea]] highlands, with special emphasis on [[iconicity]].</ref>

Home sign arises due to the absence of any other way to communicate. Within the span of a single lifetime and without the support or feedback of a community, the child naturally invents signs to help meet his or her communication needs, and may even develop a few grammatical rules for combining short sequences of signs. Still, this kind of system is inadequate for the intellectual development of a child and it comes nowhere near meeting the standards linguists use to describe a complete language. No type of home sign is recognized as a full language.<ref>The one possible exception to this is Rennellese Sign Language, which has the [[ISO 639-3]] code [rsi]. It only ever had one deaf user, and thus appears to have been a home sign system that was mistakenly-accepted into the ISO 639-3 standard. It has been proposed for deletion from the standard. ({{cite web|title=Change Request Number: 2016-002|url=http://www-01.sil.org/iso639-3/cr_files/2016-002.pdf|website=ISO 639-3|publisher=SIL International|access-date=2016-07-05|url-status=live|archive-url=https://web.archive.org/web/20160128214659/http://www-01.sil.org/iso639-3/cr_files/2016-002.pdf|archive-date=2016-01-28}})</ref>

===Primate use===
{{Main|Great ape language#Primate use of sign language|l1=Great ape language § Primate use of sign language}}

There have been several notable examples of scientists teaching signs to non-human [[primate]]s in order to communicate with [[human]]s,<ref name="MoA">{{cite book|last1=Premack and Premack|first1=David and Ann J|title=The Mind of an Ape|date=1984|publisher=W.W. Norton & Co.|location=NY|isbn=978-0393015812|edition=1st}}</ref> such as [[chimpanzee]]s,<ref name=fn1>Plooij, F.X. (1978) "Some basic traits of language in wild chimpanzees?" in A. Lock (ed.) ''Action, Gesture and Symbol'' New York: Academic Press.</ref><ref name=fn2>{{cite journal | last1 = Nishida | first1 = T | year = 1968 | title = The social group of wild chimpanzees in the Mahali Mountains | journal = Primates | volume = 9 | issue = 3| pages = 167–224 | doi=10.1007/bf01730971| hdl = 2433/213162 | s2cid = 28751730 | hdl-access = free }}</ref><ref name=fn3>{{cite journal | last1 = Premack | first1 = D | year = 1985 | title = 'Gavagai!' or the future of the animal language controversy | journal = Cognition | volume = 19 | issue = 3| pages = 207–296 | doi=10.1016/0010-0277(85)90036-8| pmid = 4017517 | s2cid = 39292094 }}</ref><ref name=fn4>{{cite journal | last1 = Gardner | first1 = R.A. | last2 = Gardner | first2 = B.T. | year = 1969 | title = Teaching Sign Language to a Chimpanzee | journal = Science | volume = 165 | issue = 3894| pages = 664–672 | doi=10.1126/science.165.3894.664| pmid = 5793972 | bibcode = 1969Sci...165..664G | citeseerx = 10.1.1.384.4164 }}</ref><ref name=fn5>Gardner, R.A., Gardner, B.T., and Van Cantfort, T.E. (1989), ''Teaching Sign Language to Chimpanzees'', Albany: SUNY Press.</ref><ref name=fn6>Terrace, H.S. (1979). ''Nim: A chimpanzee who learned Sign Language'' New York: Knopf.</ref><ref name=fn10>{{cite journal | last1 = Savage-Rumbaugh | first1 = E.S | last2 = Rumbaugh | first2 = D.M. | last3 = McDonald | first3 = K. | year = 1985 | title = Language learning in two species of apes | journal = Neuroscience and Biobehavioral Reviews | volume = 9 | issue = 4| pages = 653–665 | doi=10.1016/0149-7634(85)90012-0 | pmid = 4080283| s2cid = 579851 }}</ref> [[gorilla]]s<ref name=fn7>Patterson, F.G. and Linden E. (1981), ''The education of Koko'', New York: Holt, Rinehart and Winston</ref> and [[orangutan]]s.<ref name=fn8>Miles, H.L. (1990) "The cognitive foundations for reference in a signing orangutan" in S.T. Parker and K.R. Gibson (eds.) ''"Language" and intelligence in monkeys and apes'': Comparative Developmental Perspectives. Cambridge Univ. Press. pp. 511–539. {{doi|10.1017/CBO9780511665486.021}}. {{ISBN|9780511665486}}</ref>  However, linguists generally point out that this does not constitute knowledge of a human ''language'' as a complete system, rather than simply signs/words.<ref>
{{cite book
|last=Wallman|first=Joel
|title=Aping Language
|url=https://archive.org/details/apinglanguage00wall_0|url-access=registration|year=1992
|publisher=Cambridge University Press
|isbn=978-0-521-40666-6}}
</ref><ref>
{{cite web
 |url         = http://www.lcc.gatech.edu/~mcnair/Teaching/3206-S2004/Animal_Communication.htm
 |title       = Animal Communication
 |publisher   = Department of Linguistics, The Ohio State University
 |year        = 1994
 |access-date  = 2008-02-21
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20080207132421/http://www.lcc.gatech.edu/~mcnair/Teaching/3206-S2004/Animal_Communication.htm
 |archive-date = 2008-02-07
}}
</ref><ref>
{{cite book
|last1=Stewart|first1=Thomas W.
|last2=Vaillette|first2=Nathan
|title=Language Files: Materials for an Introduction to Language & Linguistics
|url=https://archive.org/details/languagefilesmat00stew|url-access=registration|date=2001
|publisher=The Ohio State University Press
|location=Columbus
|isbn=978-0-8142-5076-1
|pages=[https://archive.org/details/languagefilesmat00stew/page/26 26–31]
|edition=8th}}
</ref><ref>
{{cite book
|last1=Anderson|first1=Stephen R.
|title=Doctor Doolittle's Delusion
|date=2004
|publisher=Yale University Press
|location=New Haven CT
|isbn=978-0-300-10339-7
|pages=263–300}}
</ref><ref>
{{cite book
|last1=Fromkin|first1=Victoria
|last2=Rodman|first2=Robert
|last3=Hyams|first3=Nina
|title=An introduction to language
|date=2007
|publisher=Thomson Wadsworth
|location=Boston
|isbn=978-1-4130-1773-1
|pages=352–356
|edition=8th}}
</ref>  Notable examples of animals who have learned signs include:
* Chimpanzees: [[Washoe (chimpanzee)|Washoe]], [[Nim Chimpsky]] and [[Loulis (chimpanzee)|Loulis]]
* Gorillas: [[Koko (gorilla)|Koko]] and [[Michael (gorilla)|Michael]]

=== Gestural theory of human language origins ===
{{Main|Origin of language#Gestural theory|l1=Origin of language § Gestural theory}}

One theory of the evolution of human language states that it developed first as a gestural system, which later shifted to speech.<ref>{{Cite journal | doi = 10.1086/201401 | last1 = Hewes | first1 = Gordon W. | year = 1973 | title = Primate communication and the gestural origin of language | journal = Current Anthropology | volume = 14 | pages = 5–32 | s2cid = 146288708 }}</ref><ref>Harnad, S. R., Steklis, H. D., & Lancaster, J. E. (1976). Origins and evolution of language and speech. ''Annals of the New York Academy of Sciences'' 280.</ref><ref>Kimura, Doreen (1993). ''Neuromotor Mechanisms in Human Communication''. Oxford: Oxford University Press.</ref><ref>Wittmann, H. (1980). Intonation in Glottogenesis. ''The Melody of Language'' 315.</ref><ref name="Wittmann, H. 1991"/><ref>
{{Cite journal | doi = 10.1038/nn775 | last1 = Newman | first1 = A. J. | last2 = Bavelier | year = 2002 | first2 = D | last3 = Corina | first3 = D | last4 = Jezzard | first4 = P | last5 = Neville | first5 = HJ | title = A Critical Period for Right Hemisphere Recruitment in American Sign Language Processing | journal = Nature Neuroscience | volume = 5 | issue = 1| pages = 76–80 | pmid = 11753419 | s2cid = 2745545 }}</ref>  An important question for this gestural theory is what caused the shift to vocalization.<ref>Steklis, H. D., & Harnad, S. (1976). From hand to mouth: Some critical stages in the evolution of language. In Origins and evolution of language and speech (pp. 445-455). ''Annals of the New York Academy of Sciences'' 280.</ref><ref>Kolb, Bryan, and Ian Q. Whishaw (2003). ''Fundamentals of Human Neuropsychology'', 5th edition, Worth Publishers.</ref><ref>Blondin-Massé, Alexandre; Harnad, Stevan; Picard, Olivier; and St-Louis, Bernard (2013) [https://eprints.soton.ac.uk/271438/1/Harnad-Lefebvre-bookFIN-REV.pdf Symbol Grounding and the Origin of Language: From Show to Tell] {{Webarchive|url=https://web.archive.org/web/20220121152032/https://eprints.soton.ac.uk/271438/1/Harnad-Lefebvre-bookFIN-REV.pdf |date=2022-01-21 }}. In, Lefebvre, Claire; Cohen, Henri; and Comrie, Bernard (eds.) ''New Perspectives on the Origins of Language.'' Benjamin</ref>

== See also ==<!-- New links in alphabetical order please -->
{{div col|colwidth=28em}}
* [[Animal language]]
* [[Body language]]
* [[Braille]]
* [[Fingerspelling]]
* [[Phoneme#Chereme|Chereme]]
* [[Chinese number gestures]]
* [[Hearing loss]]
* [[Gang signal]]
* [[Gestures]]
* [[Intercultural competence]]
* [[International Sign]]
* [[Legal recognition of sign languages]]
* [[List of international common standards]]
* [[List of sign languages]]
* [[List of sign languages by number of native signers]]
* [[Manual communication]]
* [[Metacommunicative competence]]
* [[Modern Sign Language communication]]
* [[Origin of language]]
* [[Origin of speech]]
* [[Sign language glove]]
* [[Sign language in infants and toddlers]]
* [[Sign language media]]
* ''[[Sign Language Studies]]'' (journal)
* [[Sign name]]
* [[Sociolinguistics of sign languages]]
* [[Tactile signing]]
* [[Machine translation of sign languages]]
{{div col end}}

== References ==
{{notelist}}
{{Reflist|30em|refs=
<ref name=":2">{{cite journal | last1 = Frishberg | first1 = N | year = 1975 | title = Arbitrariness and Iconicity: Historical Change in America | journal = Language | volume = 51 | issue = 3| pages = 696–719 | doi=10.2307/412894| jstor = 412894 }}
</ref>
<ref name="Meir 2010">{{cite journal | last1 = Meir | first1 = I | year = 2010 | title = Iconicity and metaphor: Constraints on metaphorical extension of iconic forms | journal = Language | volume = 86 | issue = 4| pages = 865–96 | doi=10.1353/lan.2010.0044| s2cid = 117619041 }}</ref>
<ref name="Wilcox 2000">Wilcox, P. (2000). ''Metaphor in American Sign Language''. Washington D.C.: Gallaudet University Press.</ref>
<ref name="Wilcox 2004">{{cite journal | last1 = Wilcox | first1 = S | year = 2004 | title = Conceptual spaces and embodied actions: Cognitive iconicity and signed languages | journal = Cognitive Linguistics | volume = 15 | issue = 2| pages = 119–47 | doi = 10.1515/cogl.2004.005 }}</ref>

<!-- Not in use
<ref name=Wittmann1980>[[Henri Wittmann|Wittmann, Henri]] (1980). [http://www.nou-la.org/ling/1980a-glottogenesis.pdf "Intonation in glottogenesis"], pp. 315–29 in ''The melody of language: Festschrift Dwight L. Bolinger'', Linda R. Waugh & Cornelius H. van Schooneveld (eds.). Baltimore: University Park Press.</ref>
Not in use-->

<!-- Not in use
<ref name=Wittmann1991>{{cite journal|author=Wittmann, Henri|year=1991|title=Classification linguistique des langues signées non vocalement|journal= Revue québécoise de linguistique théorique et appliquée |volume=10|issue=1|pages= 215–88|url=http://www.nou-la.org/ling/1991a-class.pdf}}</ref>
Not in use-->

}}

== Bibliography ==
* {{Cite journal | doi = 10.1353/lan.2005.0043 | last1 = Aronoff | first1 = Mark | last2 = Meir | first2 = Irit | last3 = Sandler | first3 = Wendy | year = 2005 | title = The Paradox of Sign Language Morphology | journal = Language | volume = 81 | issue = 2| pages = 301–44 | pmid = 22223926 | pmc = 3250214 }}
* Branson, J., D. Miller, & I G. Marsaja. (1996). "Everyone here speaks sign language, too: a deaf village in Bali, Indonesia." In: C. Lucas (ed.): Multicultural aspects of sociolinguistics in deaf communities. Washington, Gallaudet University Press, pp.&nbsp;39+
* Deuchar, Margaret (1987). "Sign languages as creoles and Chomsky's notion of Universal Grammar." ''Essays in honor of Noam Chomsky'', 81–91. New York: Falmer.
* [[Karen Emmorey|Emmorey, Karen]]; & [[Harlan Lane|Lane, Harlan L.]] (Eds.). (2000). ''The signs of language revisited: An anthology to honor Ursula Bellugi and Edward Klima''. Mahwah, NJ: Lawrence Erlbaum Associates. {{ISBN|0-8058-3246-7}}.
* Fischer, Susan D. (1974). "Sign language and linguistic universals." ''Actes du Colloque franco-allemand de grammaire générative'', 2.187–204. Tübingen: Niemeyer.
* {{Cite journal | last1 = Fischer | first1 = Susan D. | year = 1978 | title = Sign languages and creoles | journal = Siple | volume = 1978 | pages = 309–31 }}
* Goldin-Meadow, Susan (2003), ''The Resilience of Language: What Gesture Creation in Deaf Children Can Tell Us About How All Children Learn Language'', Psychology Press, a subsidiary of Taylor & Francis, New York, 2003
* Gordon, Raymond, ed. (2008). ''Ethnologue: Languages of the World'', 15th edition. [[SIL International]], {{ISBN|978-1-55671-159-6|1-55671-159-X}}. {{webarchive |url=https://web.archive.org/web/20130113003139/http://www.ethnologue.com/web.asp |date=January 13, 2013 }} Sections for primary sign languages [http://www.ethnologue.com/show_family.asp?subid=90008 Browse by Language Family] and alternative ones [http://www.ethnologue.com/show_family.asp?subid=90503 Browse by Language Family].
* Groce, Nora E. (1988). ''Everyone here spoke sign language: Hereditary deafness on Martha's Vineyard''. Cambridge, Massachusetts: Harvard University Press. {{ISBN|0-674-27041-X}}.
* Healy, Alice F. (1980). "Can Chimpanzees learn a phonemic language?" In: Sebeok, Thomas A. & Jean Umiker-Sebeok, eds, Speaking of apes: a critical anthology of two-way communication with man. New York: Plenum, 141–43.
* Kamei, Nobutaka (2004). ''The Sign Languages of Africa'', "Journal of African Studies" (Japan Association for African Studies) Vol. 64, March, 2004. [NOTE: Kamei lists 23 African sign languages in this article].
* {{cite journal | last1 = Kegl | first1 = Judy | author-link = Judy Kegl | year = 1994 | title = The Nicaraguan Sign Language Project: An Overview | journal = Signpost | volume = 7 | issue = 1| pages = 24–31 }}
* [[Judy Kegl|Kegl, Judy]], Senghas A., Coppola M (1999). "Creation through contact: Sign language emergence and sign language change in Nicaragua." In: M. DeGraff (ed.), ''Comparative Grammatical Change: The Intersection of Language Acquisition, Creole Genesis, and Diachronic Syntax'', pp.&nbsp;179–237. Cambridge, Massachusetts: MIT Press.
* [[Judy Kegl|Kegl, Judy]] (2004). "Language Emergence in a Language-Ready Brain: Acquisition Issues." In: Jenkins, Lyle (ed.), ''Biolinguistics and the Evolution of Language''. John Benjamins.
* Kendon, Adam. (1988). ''Sign Languages of Aboriginal Australia: Cultural, Semiotic and Communicative Perspectives.'' Cambridge: Cambridge University Press.
* {{Cite journal | doi = 10.1525/aa.1940.42.1.02a00020 | last1 = Kroeber | first1 = Alfred L. | author-link = Alfred L. Kroeber | year = 1940 | title = Stimulus diffusion | journal = American Anthropologist | volume = 42 | pages = 1–20 | doi-access = free }}
* Lane, Harlan L. (Ed.). (1984). ''The Deaf experience: Classics in language and education''. Cambridge, Massachusetts: Harvard University Press. {{ISBN|0-674-19460-8}}.
* Lane, Harlan L. (1984). ''When the mind hears: A history of the deaf''. New York: Random House. {{ISBN|0-394-50878-5}}.
* Madell, Samantha (1998). ''Warlpiri Sign Language and Auslan&nbsp;– A Comparison''. M.A. Thesis, Macquarie University, Sydney, Australia. {{webarchive |url=https://web.archive.org/web/20110608171315/http://members.ozemail.com.au/~gamgee/writing_handtalk.html |date=June 8, 2011 }}
* Madsen, Willard J. (1982), ''Intermediate Conversational Sign Language''. Gallaudet University Press. {{ISBN|978-0-913580-79-0}}.
* O'Reilly, S. (2005). ''Indigenous Sign Language and Culture; the interpreting and access needs of Deaf people who are of Aboriginal and/or Torres Strait Islander in Far North Queensland''. Sponsored by ASLIA, the Australian Sign Language Interpreters Association.
* [[Carol Padden|Padden, Carol]]; & [[Tom Humphries|Humphries, Tom]]. (1988). ''Deaf in America: Voices from a culture''. Cambridge, Massachusetts: Harvard University Press. {{ISBN|0-674-19423-3}}.
* Pfau, Roland, Markus Steinbach & Bencie Woll (eds.), ''Sign language. An international handbook (HSK – Handbooks of linguistics and communication science).'' Berlin: Mouton de Gruyter.
* Poizner, Howard; Klima, Edward S.; & Bellugi, Ursula. (1987). ''What the hands reveal about the brain''. Cambridge, Massachusetts: MIT Press.
* [[David Premack|Premack, David]], & Ann J. Premack (1983). ''[[The mind of an ape]]''. New York: Norton.
* {{Cite journal | doi = 10.1016/0010-0277(85)90036-8 | last1 = Premack | first1 = David | author-link = David Premack | year = 1985 | title = 'Gavagai!' or the future of the animal language controversy | journal = Cognition | volume = 19 | issue = 3| pages = 207–96 | pmid = 4017517 | s2cid = 39292094 }}
* [[Oliver Sacks|Sacks, Oliver W.]] (1989). ''[[Seeing Voices|Seeing voices: A journey into the world of the deaf]]''. Berkeley: University of California Press. {{ISBN|0-520-06083-0}}.
* Sandler, Wendy (2003). "Sign Language Phonology". In William Frawley (Ed.), The Oxford International Encyclopedia of Linguistics.[http://sandlersignlab.haifa.ac.il/pdf/Sign%20Language%20Phonology%20OEL.pdf]
* Sandler, Wendy & Lillo-Martin, Diane (2001). "Natural sign languages". In M. Aronoff & J. Rees-Miller (Eds.), ''Handbook of linguistics'' (pp.&nbsp;533–562). Malden, MA: Blackwell Publishers. {{ISBN|0-631-20497-0}}.
* Stiles-Davis, Joan; Kritchevsky, Mark; & Bellugi, Ursula (Eds.). (1988). ''Spatial cognition: Brain bases and development''. Hillsdale, NJ: L. Erlbaum Associates. {{ISBN|0-8058-0046-8}}; {{ISBN|0-8058-0078-6}}.
* [[William C. Stokoe|Stokoe, William C.]] (1960, 1978). ''Sign language structure: An outline of the visual communication systems of the American deaf''. Studies in linguistics, Occasional papers, No. 8, Dept. of Anthropology and Linguistics, University at Buffalo. 2d ed., Silver Spring: Md: Linstok Press.
* [[William C. Stokoe|Stokoe, William C.]] (1974). Classification and description of sign languages. Current Trends in Linguistics 12.345–71.
* Twilhaar, Jan Nijen, and Beppie van den Bogaerde. 2016. ''Concise Lexicon for Sign Linguistics''. John Benjamins Publishing Company.
* Valli, Clayton, Ceil Lucas, and Kristin Mulrooney. (2005) ''Linguistics of American Sign Language: An Introduction'', 4th Ed. Washington, DC: Gallaudet University Press.
* Van Deusen-Phillips S.B., Goldin-Meadow S., Miller P.J., 2001. ''Enacting Stories, Seeing Worlds: Similarities and Differences in the Cross-Cultural Narrative Development of Linguistically Isolated Deaf Children'', Human Development, Vol. 44, No. 6.
* Wilbur, R.B. (1987). ''American Sign Language: Linguistic and applied dimensions''. San Diego, CA: College-Hill.

== Further reading ==
* [[Margalit Fox|Fox, Margalit]] (2007) ''Talking Hands: What Sign Language Reveals About the Mind '', [[Simon & Schuster]] {{ISBN|978-0-7432-4712-2}}
* Quenqua, Douglas. [https://www.nytimes.com/2012/12/04/science/sign-language-researchers-broaden-science-lexicon.html Pushing Science's Limits in Sign Language Lexicon], ''[[The New York Times]]'', December 4, 2012, p. D1 and published online at NYTimes.com on December 3, 2012. Retrieved on December 7, 2012.

== Academic journals related to sign languages ==
* ''[[American Annals of the Deaf]]'', [[Gallaudet University Press]]
* ''[http://journalofasl.com/ Journal of American Sign Language and Literature]'', [http://aslized.org/ ASLized!]
* ''[[Journal of Deaf Studies and Deaf Education]]'', [[Oxford University Press]]
* ''[[Sign Language Studies]]'', [[Gallaudet University Press]]
* ''[https://benjamins.com/#catalog/journals/sll/main Sign Language & Linguistics]'', [[John Benjamins Publishing Company]]

== External links ==
{{Sister project links|commons=category:Sign language|b=American Sign Language|voy=no|species=no|n=no|wikt=sign language|d=y|q=no|s=no}}

''Note: the articles for [[List of sign languages|specific sign languages]] (e.g. [[American Sign Language|ASL]] or [[British Sign Language|BSL]]) may contain further external links, e.g. for learning those languages.''
* [http://lsf.wikisign.org/wiki/Langue:Signes_du_Monde Langue:Signes du Monde], directory for all online Sign Languages dictionaries {{in lang|fr|en}}
* [https://listserv.linguistlist.org/pipermail/slling-l/ List Serv for Sign Language Linguistics] {{webarchive |url=https://web.archive.org/web/20041013082721/http://listserv.linguistlist.org/archives/slling-l.html |date=2004-10-13}}
* [http://www.musslap.zcu.cz/en/about-project/ The MUSSLAP Project], Multimodal Human Speech and Sign Language Processing for Human-Machine Communication
* Mallery, Garrick. 1879–1880. [http://www.gutenberg.org/files/17451/17451-h/17451-h.htm Sign Language among North American Indians, by Garrick Mallery.] ''Sign language among North American Indians compared with that among other peoples and deaf-mutes. A first annual report of the Bureau of Ethnology to the Secretary of the [[Smithsonian Institution]]''. [[Project Gutenberg]].''
* [https://tv.signlangtv.org/ signlangtv.org], a project documenting sign language television shows for the deaf around the world
* {{Curlie|Science/Social_Sciences/Linguistics/Languages/Natural/Sign_Languages/}}

{{Sign language navigation}}
{{Authority control}}

{{Nonverbal communication}}

{{DEFAULTSORT:Sign Language}}
[[Category:Sign language| ]]
[[Category:Sign languages| ]]
[[Category:Language varieties and styles]]
[[Category:Deafness]]
[[Category:Deaf culture]]
[[Category:Education for the deaf]]
[[Category:Articles containing video clips]]