01 n. Power to produce effects; operation or energy of an agent or force; production of the effect intended; as, the efficacy of medicine in coun…
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1.
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.
Syn.
efficacy. — Syn. -- Virtue; force; energy; potency; efficiency.