Non-Manual Features

The facial expressions, mouth movements, eye gaze, head tilts, and body postures that convey grammatical and semantic information in sign languages, functioning alongside manual hand signs. Non-manual features can indicate questions (raised eyebrows), negation (head shake), topic marking, relative clauses, and emotional content. In signing avatar and motion capture research, accurately reproducing non-manual features remains technically challenging but is essential for intelligibility—signs that differ only in mouth movement (homonyms) can have completely different meanings.