Sign language: A language that employs signs made with the hands and other movements, including facial expressions and postures of the body, used primarily by people who are deaf. There are many different sign languages as, for example, British and American sign languages. British sign language (BSL) is not easily intelligible to users of American sign language (ASL). Unlike ASL, BSL uses a two-handed alphabet. In developing countries, deaf people may use the sign language of educators and missionaries from elsewhere in the world. For example, some deaf individuals in Madagascar use Norwegian sign language. By contrast, deaf children in Nicaragua have created their own sign language. Study of the emerging Nicaruagan sign language (NSL) has revealed that children naturally possess learning abilities capable of giving language its fundamental structure. See also: American sign language.