Non-manual markers

Linguistic features in sign languages that are conveyed through facial expressions, head tilts, eye gaze direction, mouth movements, and body posture rather than through hand signs. Non-manual markers serve grammatical functions in ASL and other sign languages — including marking questions, negation, topics, and relative clauses — making them essential for grammatically correct and comprehensible signing. ASL learners frequently struggle with non-manual markers, and automated signing assessment systems must be able to evaluate facial expressions and head movements alongside hand position to provide accurate feedback.