ef·fi·ca·cy n. Power to produce effects; operation or energy of an agent or force; production of the effect intended; as, the efficacy of medicine in counteracting disease; the efficacy of prayer. “Of noxious efficacy.”
Syn: -- efficacy.
Syn: -- Virtue; force; energy; potency; efficiency.
n : capacity or power to produce a desired effect; "concern
about the safety and efficacy of the vaccine" [syn: efficaciousness]