efficacy

[ ef-i-kuh-see ]

noun

, plural ef·fi·ca·cies.

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. Compare effectiveness ( def 3 ).

efficacy

/ ˈɛfɪkəsɪ /

noun

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

Other Words From

• non·ef·fi·ca·cy 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 )

Related Words

• adequacy
• competence
• effectiveness
• potency
• virtue