operative

(noun) a person secretly employed in espionage for a government. Synonyms: secret agent, intelligence officer, intelligence agent.

(noun) someone who can be employed as a detective to collect information. Synonyms: private detective, PI, private eye, private investigator, shamus, sherlock.

(adj) being in force or having or exerting force. Synonyms: operative (vs. inoperative). Examples: "Operative regulations." "The major tendencies operative in the american political system."

(adj) relating to or requiring or amenable to treatment by surgery especially as opposed to medicine. Synonyms: surgical (vs. medical). Examples: "A surgical appendix." "A surgical procedure." "Operative dentistry."

(adj) effective; producing a desired effect. Example: "The operative word."

(adj) (of e.g. a machine) performing or capable of performing. Synonyms: running(prenominal), functional, working(prenominal). Examples: "In running (or working) order." "A functional set of brakes."