Wikipedia Reference Information
A sign language (also signed language) is a language which uses manual communication, body language and lip patterns instead of sound to convey meaning—simultaneously combining hand shapes, orientation and movement of the hands, arms or body, and facial expressions to express fluidly a speaker's thoughts. Sign languages commonly develop in deaf communities, which can include interpreters and friends and families of deaf people as well as people who are deaf or hard of hearing themselves. They are also used by people with speech impairments such as Aphasia.
As is the case in spoken language, sign language differs from one region to another. However, when people using different signed languages meet, communication is significantly easier than when people of different spoken languages meet. Sign language, in this respect, gives access to an international deaf community. Sign language is however not universal, and many different sign languages exist that are mostly mutually unintelligible.
Wherever communities of deaf people exist, sign languages develop, in fact their complex spatial grammars are markedly different than spoken language. In many cases, various signed "modes" of spoken languages have been developed, such as Signed English and Warlpiri Sign Language. Hundreds of sign languages are in use around the world and are at the core of local Deaf cultures. Some sign languages have obtained some form of legal recognition, while others have no status at all.
Exemplary for the mature status of sign languages is the growing body of sign language poetry, and other stage performances. The poetic mechanisms available to signing poets are not all available to a speaking poet. This offers new, exciting ways for poems to reach and move the audience.
The complete, up-to-date and editable article about Sign Language can be found at Wikipedia: Sign Language