A gesture is a form of communication in which bodily actions communicate particular messages [1].

Manual gestures are most commonly broken down into four distinct categories:

• Symbolic (Emblematic): a handwave used for "hello."
• Deictic (Indexical): a pointing finger showing “this” or “that.”
• Motor (Beat): accompanying the prosody of speech.
• Lexical (Iconic): a gesture that depicts the act of throwing may be synchronous with the utterance, "He threw the ball right into the window."

Speech can be described as audible movements, a series of vocal gesture (Löfqvist 1990). By varying the positions and trajectories of the lips, the jaw, the tongue, the velum and the glottis, a speaker creates variations in air pressure and airflow in the vocal tract. These variations in pressure and flow produce the acoustic signal that we hear when listening to speech. “Speech is rather a set of movements made audible than a set of sounds produced by movements” (Stetson 1905).

Language is thought by some scholars to have evolved in Homo sapiens from an earlier system consisting of manual gestures (Corballis 2005).