operative

/ˈä-p(ə-)rə-tiv/

Middle English operatif "active, working," borrowed from Late Latin operātīvus, from operātus, past participle of operārī "to work, be efficacious" + Latin -īvus -ive

adjective

  1. producing an appropriate effect : efficacious

  2. most significant or essential

  3. exerting force or influence : operating

operative techniques

the operative word in a phrase

noun

  1. operator: such as

  2. artisan, mechanic

  3. a secret agent