ef·fi·ca·cy /ˈɛfɪkəsi/
  功效,效力
  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.
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  efficacy
       n : capacity or power to produce a desired effect; "concern
           about the safety and efficacy of the vaccine" [syn: efficaciousness]
           [ant: inefficacy]