1) At work 2) Effective 3) Having an effect 4) In effect 5) In running order 6) Operating 7) Operative 8) Producing an effect 9) Producing effects 1) Operative 
• (a.) Operative. • (n.) An operative person or thing.
In conditioning, any behaviour or specific response chosen by the experimenter; its frequency is intended to increase or decrease by the judicious pairing with it of a reinforcer when it occurs. ... Synonym: target behaviour, target response. ... (05 Mar 2000) ... 
(op´әr-әnt) in psychology, said of a response not elicited by specific external stimuli but that recurs at a given rate under particular circumstances. See operant conditioning.
Op'er·ant adjective [ Latin operans , present participle of operari . See Operate .] Operative. [ R.] Shak. -- noun An operative person or thing. [ R.] Coleridge. 
Type: Term Pronunciation: op′ĕr-ănt Definitions: 1. In conditioning, any behavior or specific response chosen by the experimenter; its frequency is intended to increase or decrease by the judicious pairing with it of a reinforcer when it occurs. Synonyms: target behavior1, target response
adjective having influence or producing an effect; `many emotional determinants at work`; `an operant conscience`
Behavior emitted by an organism that can be characterized in terms of the observable effects it has on the environment.
operating; producing effects.
having influence or producing an effect