Sign language on television

A sign language (also signed language) is a language which chiefly uses manual communication to convey meaning, as opposed to acoustically conveyed sound patterns. This can involve simultaneously combining hand shapes, orientation and movement of the hands, arms or body, and facial expressions to express a speaker's thoughts. Sign languages share many similarities with spoken languages (sometimes called "oral languages"), which depend primarily on sound, and linguists consider both to be types of natural language. Although there are some significant differences between signed and spoken languages, such as how they use space grammatically, sign languages show the same linguistic properties and use the same language faculty as do spoken languages. They should not be confused with body language, which is a kind of non-linguistic communication.

Wherever communities of deaf people exist, sign languages have developed, and are at the cores of local deaf cultures. Although signing is used primarily by the deaf, it is also used by others, such as people who can hear but cannot physically speak, or have trouble with spoken language due to some other disability (augmentative and alternative communication).

It is not clear how many sign languages there are. A common misconception is that all sign languages are the same worldwide or that sign language is international. Aside from the pidgin International Sign, each country generally has its own, native sign language, and some have more than one (although there are also substantial similarities among all sign languages). The 2013 edition of Ethnologue lists 137 sign languages. Some sign languages have obtained some form of legal recognition, while others have no status at all.

Linguists distinguish natural sign languages from other systems that are precursors to them or derived from them, such as invented manual codes for spoken languages, home sign, "baby sign", and signs learned by non-human primates.

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