operant (adj.)

"that works, working, engaged in action," early 15c., from Latin operantem (nominative operans), present participle of operari "to work, labor" (in Late Latin "to have effect, be active, cause"), from opera "work, effort," related to opus (genitive operis) "a work" (from PIE root *op- "to work, produce in abundance"). Psychological sense of "involving behavior modification" coined 1937 by U.S. psychologist B.F. Skinner (as in operant conditioning, 1938, Skinner).