Sign languages (also known as signed languages) are languages that use manual communication to convey meaning. This can include simultaneously employing hand gestures, movement, orientation of the fingers, arms or body, and facial expressions to convey a speaker's ideas. Sign languages often share significant similarities with their respective spoken language, such as American Sign Language (ASL) with American English. Grammar and sentence structure, however, may vary to encourage efficiency and fluidity in speaking. It is important to note that just because a spoken language is intelligible transnationally, such as English in the United States and the United Kingdom, does not mean that the sign languages from those regions are as well; ASL and British Sign Language (BSL) were formed independently and are therefore unintelligible.
Linguists consider both spoken and signed communication to be types of natural language, meaning that both emerged through an abstract, protracted aging process and evolved over time without meticulous planning. Sign language should not be confused with "body language ", a type of nonverbal 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 and hard of hearing, it is also used by hearing individuals, such as those unable to physically speak, or those who have trouble with spoken language due to a disability or condition (augmentative and alternative communication ).
It is unclear how many sign languages currently exist worldwide.
