Any means of communication through bodily movements, especially of the hands and arms, rather than through speech.
It has long been used by speakers of mutually unintelligible languages
for example, various Plains Indian tribes in 19th-century North America communicated via a sign language
and is widely used for communication by the deaf. Charles-Michel, abbé de l'Épée (1712–89), developed the first sign language for the deaf in the mid-18th century; his system developed into French Sign Language (FSL), still used in France. Transported to the U.S. in 1816 by Thomas Gallaudet (1787–1851), it evolved into American Sign Language (ASL, or Ameslan), now used by more than half a million people. These and other national sign languages generally express concepts rather than elements of words and thus have more in common with each other than with their countries' spoken languages.