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

An employee or other worker with some particular function or skill. / A spy, secret agent, or detective. / A participant in an operation.

simple past tense and past participle of operate

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

plural of operative

Third-person singular simple present indicative form of operate

plural of opera

plural of operator

plural of operant

Able to be operated or used / Able to be put into operation; practicable / Able to be treated by surgery