From Longman Dictionary of Contemporary Englishefficaciousef‧fi‧ca‧cious /ˌefəˈkeɪʃəs◂/ adjective formal EFFECTIVEworking in the way you intended SYN effective an equally efficacious method of treatment
Examples from the Corpus
efficacious• Some found bathing the patient in a bath of nitric acid to be efficacious!• This, as almost always, proved efficacious.• If we did, we would be forced to choose between enormous guilt and efficacious action.• Areas where safeguards developed against the backdrop of a different type of decision-making may be more efficacious and apposite.• The cedar lining that once protected fine cigars from deteriorating is equally efficacious at preserving cardboard rectangles from insect damage.• He sees the present as the open door to an efficacious future.• On seeing the Muybridge article he must immediately have been convinced that photography was the most efficacious means of advancing his researches.• This suggests that improving access to dietitians might be more efficacious than other changes.• More efficacious treatments may soon be available.Origin efficacious (1500-1600) Latin efficax, from efficere; → EFFECT1 