- operation
- late 14c., "action, performance, work," also "the performance of some science or art," from O.Fr. operacion, from L. operationem (nom. operatio) "a working, operation," from operari "to work, labor" (in L.L. "to have effect, be active, cause"), from opera "work, effort," related to opus (gen. operis) "a work" (see opus). The surgical sense is first attested 1597. Military sense of "series of movements and acts" is from 1749.