Definition of "Operative" :

noun: someone who can be employed as a detective to collect information

noun: a person secretly employed in espionage for a government

adjective: being in force or having or exerting force

"Operative regulations."

adjective: (of e.g. a machine) performing or capable of performing

adjective: relating to or requiring or amenable to treatment by surgery especially as opposed to medicine

"Operative dentistry."

adjective: effective; producing a desired effect

"The operative word."