That operates to produce an effect.
Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment.
An operative person or thing.
Producing the appropriate or designed effect; efficacious.
Functional, in working order.
Effectual or important.
Having the power of acting; hence, exerting force, physical or moral; active in the production of effects.
Based upon, or consisting of, a surgical operation or operations.
An employee or other worker with some particular function or skill.
A spy, secret agent, or detective.
A participant in an operation.