Refers to the method or system of communication using hand gestures and facial expressions, often in the context of deaf education or linguistics.
彼女は手話法を使って聴覚障害者と会話した。
She communicated with the hearing-impaired person using sign language.
Compound of 手話 (sign language) and 法 (method, law). The exact historical derivation is uncertain, but the term likely emerged in the context of deaf education.