noun, plural ef·fi·ca·cies.
Origin of efficacy
Related Words for efficacyadequacy, effectiveness, competence, virtue, potency, vigor, use, strength, force, ability, power, efficaciousness, energy, influence, effect, weight, capability, performance, success, sufficiency
Examples from the Web for efficacy
Contemporary Examples of efficacy
On average, the vaccine has an efficacy of about 60 percent.When You Get the Flu This Winter, You Can Blame Anti-Vaxxers
January 1, 2015
The efficacy of bandying threats of going to hell met its match in the Civil War.Americans’ Burning Obsession With Hell
September 26, 2014
Most Pennsylvanians now support a moratorium on capital punishment until its efficacy can be determined.Pennsylvania’s Lethal Injection Fiasco
September 18, 2014
But the conditions on the ground in Syria are not the same, and cast great doubt on the efficacy of airstrikes.Why Airstrikes in Syria Won't Work
Rep. Adam Schiff
September 4, 2014
The State Department emphasized American assistance for the rebels; the White House downplayed the efficacy of that assistance.Obama Stifled Hillary’s Syria Plans and Ignored Her Iraq Warnings for Years
August 14, 2014
Historical Examples of efficacy
Much has been said concerning the efficacy of the Water Fly as a lure.
A few tears mingled with the draught, and perhaps gave it all its efficacy.The Man of Adamant
He no more believes in the efficacy of soap than in the efficacy of a good reputation.The Book of Khalid
All races have uttered this prayer, apparently with a firm belief in its efficacy.Sex=The Unknown Quantity
Day by day her faith in the efficacy of her petitions had grown upon her.Tess of the Storm Country
Grace Miller White
1520s, from Latin efficacia "efficacy, efficiency," from efficax (genitive efficacis) "powerful, effective," from stem of efficere "work out, accomplish" (see effect). Earlier in same sense was efficace (c.1200), from Old French eficace (14c.), from Latin efficacia; also efficacite (early 15c.), from Latin efficacitatem.