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, where Socratessays: "If we hadn't a voice or a tongue, and

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In linguistic terms, sign languages are as rich and complex as any spoken language, despite the common misconception that they are not "real languages". Professional linguistshave studied many sign languages and found that they exhibit the fundamental properties

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Deaf communities and Deaf culture
When Deaf people constitute a relatively small proportion of the general population, Deaf communities often

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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

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• Aronoff, Mark; Meir, Irit; Sandler, Wendy (2005). "The Paradox of Sign Language Morphology". Language. 81 (2): 301–44. doi:10.1353/lan.2005.0043. PMC 3250214. PMID 22223926.
• Branson, J., D. Miller, & I G. Marsaja. (1996). "Everyone here speaks sign language, too: a deaf

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• Fox, Margalit (2007) Talking Hands: What Sign Language Reveals About the Mind , Simon & Schuster ISBN 978-0-7432-4712-2
• Quenqua, Douglas. Pushing Science's Limits in Sign Language Lexicon, The New York Times, December 4, 2012, p. D1 and published online at

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• Animal language
• Body language
• Braille
• Fingerspelling

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