efficacy

Sometimes ef·fi·cac·i·ty

[ef-i-kuh-see]

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.

efficacy

/ ˈɛfɪkəsɪ /

noun

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

Other Word Forms

• nonefficacy noun

Word History and Origins

Origin of efficacy¹

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

But when it comes to the usefulness of AI agents, an important demonstration of efficacy has been established by some first movers in the market.

Read more on The Wall Street Journal

The Merck pill, which inhibits PCSK9, showed comparable efficacy to existing injectable drugs and did not have increased side effects or study dropouts.

Read more on Barron's

Meta’s AI spending will undoubtedly improve the efficacy of its advertising products and allow the company to charge more, he acknowledged.

Read more on MarketWatch

With no apparent distance limitations, the missile is meant to get around Western air defense systems, though nuclear scientists doubt the missile’s efficacy.

Read more on The Wall Street Journal

Under the new law, counties can continue to harvest data about the efficacy of their own CalFresh programs.

Read more on Los Angeles Times

Related Words

• adequacy 
• competence 
• effectiveness 
• potency 
• virtue