Effectual or important. / Functional, in working order. / Having the power of acting; hence, exerting force, physical or moral; active in the production of effects.

In operation; that operates. / Involved in an operation.

present participle and gerund of operate

(in combination) operated by the means specified e.g. a battery-operated toy / having undergone an operation

simple past tense and past participle of operate

plural of operative

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

That operates to produce an effect.

Third-person singular simple present indicative form of operate

plural of opera