operant

Adjective

 * 1) That operates to produce an effect.
 * 2) * 1955, Rex Stout, "When a Man Murders...", in Three Witnesses, October 1994 Bantam edition, ISBN 0553249592, page 117:
 * I tell you frankly, if Paul Aubry is guilty I hope is convicted and punished; but if one of the others is guilty I hope he—or she—is punished, and if I knew anything operant to that end I certainly would not withhold it.
 * I tell you frankly, if Paul Aubry is guilty I hope is convicted and punished; but if one of the others is guilty I hope he—or she—is punished, and if I knew anything operant to that end I certainly would not withhold it.

Noun

 * 1) An operative person or thing.
 * 2)  Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment.

Etymology
.