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. -- Ef`fi*ca"cious*ness, n.