ef`fi*ca"cious*ly
Webster's Dictionary (GCIDE)
Efficacious \Ef`fi*ca"cious\, a. [L. eficax, -acis, fr. efficere. See Effect, n.] Possessing the quality of being effective; productive of, or powerful to produce, the effect intended; as, an efficacious law.
Syn: See Effectual. -- Ef`fi*ca"cious*ly, adv. [1913 Webster]