A sign language (also signed language) is a language which, instead of acoustically conveyed sound patterns, uses visually transmitted sign patterns (manual communication, body language) to convey meaning—simultaneously combining hand shapes, orientation and movement of the hands, arms or body, and facial expressions to fluidly express a speaker's thoughts.
Wherever communities of deaf people exist, sign languages develop. Their complex spatial grammars are markedly different from the grammars of spoken languages.
Hundreds of sign languages are in use around the world and are at the cores of local deaf cultures. Some sign languages have obtained some form of legal recognition, while others have no status at all.
History of sign language
One of the earliest written records of a signed language occurred in the fifth century BC, in Plato's 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?"
It seems that groups of deaf people have used signed languages throughout history.
In 2nd-century Judea, the recording in the Mishnah tractate Gittin stipulated that for the purpose of commercial transactions "A deaf-mute can hold a conversation by means of gestures. Ben Bathyra says that he may also do so by means of lip-motions." This teaching was well known in Jewish society where study of Mishnah was compulsory from childhood.
In 1620, Juan Pablo Bonet published 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.
It is considered the first modern treatise of Phonetics and Logopedia, setting out a method of oral education for the deaf people by means of the use of manual signs, in form of a manual alphabet to improve the communication of the mute or deaf people.
From the language of signs of Bonet, Charles-Michel de l'Épée published his manual alphabet in the 18th century, which has survived basically unchanged in France and North America until the present time.
Sign languages have often evolved around schools for deaf students. 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.
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.
Linguistics of signIn linguistic terms, sign languages are as rich and complex as any oral language, despite the common misconception that they are not "real languages". Professional linguists have studied many sign languages and found them to have every linguistic component required to be classed as true languages.
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.
Nor are they a visual rendition of an oral language. They have complex grammars of their own, and can be used to discuss any topic, from the simple and concrete to the lofty and abstract.
Sign languages, like oral languages, organize elementary, meaningless units (phonemes; once called cheremes in the case of sign languages) into meaningful semantic units. The elements of a sign are Handshape (or Handform), Orientation (or Palm Orientation), Location (or Place of Articulation), Movement, and Non-manual markers (or Facial Expression), summarised in the acronym HOLME.
Common linguistic features of deaf sign languages are extensive use of classifiers, a high degree of inflection, and a topic-comment syntax. Many unique linguistic features emerge from sign languages' ability to produce meaning in different parts of the visual field simultaneously. For example, the recipient of a signed message can read meanings carried by the hands, the facial expression and the body posture in the same moment. This is in contrast to oral languages, where the sounds that compose words are mostly sequential (tone being an exception).