operative (adj.) Look up operative at Dictionary.com
"producing the intended effect," early 15c., from Old French operatif (14c.) or directly from Late Latin operativus "creative, formative," from operat-, past participle stem of operari (see operation). Weakened sense of "significant, important" is from 1955.
operative (n.) Look up operative at Dictionary.com
"worker, operator," 1809, from operative (adj.); sense of "secret agent, spy" is first attested 1930, probably from its use by the Pinkerton Detective Agency as a title for their private detectives (1905).