Sign language

Sign language was a gestural means of communication used by humanoids and other species. It was a language primarily used by those unable to speak — either through deafness or by lacking a larynx — and by races that used gestures to supplement orally-conveyed information.

Hand signals and gestures predated speech in many cultures. 

Many different forms of sign language have been developed. Some forms were made for use in combat, sometimes designed so as to be difficult to interpret even when read by imaging sensors. 

Chimpanzees were taught a form of sign language on Earth, one which was similar to that used by the Isitri. 

History
10,000 years ago, colonial Herculese began enslaving the native Yerba. After birth, their speech centers were surgically removed, forcing them to communicate exclusively with sign language. 

In 2249, when Nyota Uhura was 10 years old, she learned to sign in order to communicate with her deaf cousin Epala. It spurred an interest in the field of communications. 

In 2266, a signing message from captured Yerba Queen Germal was projected onto clouds so that her people could all see the message. She had been ordered to sign a surrender message, but to prevent the genocide of her race she instead ordered a declaration of war against the Herculese. 

In 2267, Nyota Uhura was temporarily assigned to the USS Lexington (NCC-1709) to serve as an interpreter for Commodore Robert Wesley on a diplomatic mission to Rithra. Rithram communication was oral but supplemented with gestures which the universal translator could not translate. 

In 2269, Ensign Sara George from the USS Enterprise (NCC-1701) recorded personality scans of natives on Kyros. To get close enough to set up the equipment, she behaved like she was mute, communicated with sign language, and ented a room at an inn. The scans fed data into telescan cephalic implants. 

In 2270, Chista served as an interpreter for a landing party from the Enterprise to Isitra Zero. The telepathic Isitri had simplistic speech centers, and developed gestural languages for those born without telepathic capabilities. Many Isitri were deaf. 

In 2365, the Federation starship USS Enterprise (NCC-1701-D) took the deaf-mute mediator Riva to Solais V to lead a delicate peace negotiation. He expected to be able to use his telepathic 'chorus' to talk, but they were murdered by a dissident. Data became fluent in five sign languages to communicate with Riva and serve as his replacement interpreter. But Riva improvised instead, intending to teach sign language to both sides and create a common experience between them. 

After 2368, universal translators were updated to record tonal and gestural information, with input from Sofia Borges from her research on the Tomarian language, which had layers of meaning contained in vocal pitch, gesture and posture. (SS TNG (Friends With the Sparrows))

In 2372, Jake Sisko and Tol Elliena used sign language to communicate with rapidly-growing children on a generational colony ship from the Andromeda Galaxy. 

Sign language users

 * Chista
 * Data (Starfleet)
 * Governor Endris (Rithra)
 * Epala (Earth
 * Queen Germal (Hercula)
 * General Mynota
 * Riva
 * Sketel (Isitra Zero)
 * Soral
 * Sa-Gahnesaam (Odib)
 * Nyota Uhura (Earth)

Signing species

 * Breen
 * Isitri
 * Pak'shree
 * Rithram
 * Yerba