efficacy

American  

[ef-i-kuh-see] / ˈɛf ɪ kə si /

Sometimes efficacity

noun

PLURAL

efficacies

1. the capacity for producing a desired result or effect.

   Short, frequent periods of practice were shown to have greater efficacy than longer and less frequent ones.

2. a measure of the success of a vaccine or other pharmaceutical when used in the controlled environment of a clinical trial, as opposed to in the real world.

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efficacy British  

/ ˈɛfɪkəsɪ /

noun

1. the quality of being successful in producing an intended result; effectiveness

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Other Word Forms

• nonefficacy noun

Etymology

Origin of efficacy

First recorded in 1520–30; from Latin efficācia, from efficāc- (stem of efficāx ) “effective, effectual” + -ia, noun suffix; efficacious ( def. ), -y ³ ( def. )

Example Sentences

We at least don’t have to guess about the efficacy of their manipulations.

From The Wall Street Journal

Both their efficacy and side effects can wane as the days go by until the next shot.

From The Wall Street Journal

“We want our brand to be a beacon for younger consumers who seek greater efficacy, ingredient-led innovation, modern packaging and compelling storytelling,” she said in an email.

From The Wall Street Journal

Now, doctors screen newborns for spinal muscular atrophy, and Zolgensma has shown efficacy at preventing progression External link of the disease over the long term.

From Barron's

With security experts questioning the efficacy of megaprisons and other hardline measures on crime, voters might soon grow disillusioned with the lack of real progress, he said.

From The Wall Street Journal

Related Words

• adequacy
• competence
• effectiveness
• potency
• virtue