EFFICACY
Ef"fi*ca*cy, n. Etym: [L. efficacia, fr. efficax. See Efficacious.]
Defn: 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." Milton.
Syn.
— Virtue; force; energy; potency; efficiency.
EFFICIENCE; EFFICIENCY
Ef*fi"cience, Ef*fi"cien*cy, n. Etym: [L. efficientia.]
1. The quality of being efficient or producing an effect or effects; efficient power; effectual agency. The manner of this divine efficiency being far above us. Hooker.
2. (Mech.)
Defn: The ratio of useful work to energy expended. Rankine. Efficiency of a heat engine, the ratio of the work done an engine, to the work due to the heat supplied to it.
EFFICIENT Ef*fi"cient, a. Etym: [L. efficiens, -entis, p. pr. of efficere to effect: cf. F. efficient. See Effect, n.]
Defn: Causing effects; producing results; that makes the effect to be what it is; actively operative; not inactive, slack, or incapable; characterized by energetic and useful activity; as, an efficient officer, power. The efficient cause is the working cause. Wilson.
Syn.
— Effective; effectual; competent; able; capable; material; potent.