(of things, not of people 指物，不指人 producing the result that was wanted or intended 有效的；奏效的；灵验的 They hope the new drug will prove especially efficacious in the relief of pain. 他们希望这种新药能在缓解疼痛方面产生特效。 🔊🔊
Word Originearly 16th cent.: from Latin efficax, efficac- (from efficere ‘accomplish’, from ex- ‘out, thoroughly’ + facere ‘do, make’) + -ious.