In spoken language, words are produced by using the mouth and voice to make sounds. But for people who are Deaf (particularly those who are profoundly deaf), the sounds of speech are often not heard, and only a fraction of speech sounds can be seen on the lips.

Sign languages are based on the idea that vision is the most useful tool a deaf person has to communicate and receive information.

In contrast to the linear presentation of spoken languages, ASL is an extremely complex semantically based visual-spatial language. (The word “run” in English has a documented 150 signs depending on its meaning).

ASL as a language that is completely separate and distinct from English does contain all the fundamental features of language:  rules for pronunciation, word order, and complex grammar.

In terms of syntax, for example, ASL has a Topic-Comment structure, while English uses Subject–Verb-Object. The word/sign order in ASL, and the signs themselves, can change to express grammatical relationships.

ASL has multiple information bits inside the formation of one sign. This multiple segmentation makes it an exciting language for linguists to study and a frustrating language for Deaf-impaired (aka, Hearing) people to learn.

Every language has ways of signaling different functions, such as asking a question rather than making a statement. For example, English speakers ask a question by raising the pitch of their voice; ASL users ask a question by raising their eyebrows, widening their eyes, and tilting their bodies forward.

ASL signs employ handshape, position, and movement; shifts and movements in body orientation, facial expressions (such as eyebrow motions, eye gaze, head tilt, and lip-mouth movements and more), size, speed, and direction of movement and other visual cues to form individual and compound signs.