The interpretation of body language, such as facial expressions and gestures, or more formally non-verbal behaviour related to movement of any part of the body, is technically known as

Interpretation of body language such as facial expressions and gestures, and movement of any body part, is technically kinesics.

Kinesics reads meaning from posture, gaze shifts and limb movement as a channel of non-verbal behaviour.

Voice cues that ride alongside spoken words, such as pitch and tone, belong to para-language, not to body movement.

The study of speech sounds themselves is phonetics, concerned with articulation rather than gestures.

The informal chain of rumour spreading through an organisation is the grapevine, a channel not a body-language study.

Ray Birdwhistell coined kinesics to name the systematic study of bodily communication.