First Known Use: 13th century
Dictionary
efficacy
efficacy
noun ef·fi·ca·cy \ˈe-fi-kə-sē\
: the power to produce a desired result or effect
plural ef·fi·ca·cies
Full Definition of EFFICACY
: the power to produce an effect
See efficacy defined for English-language learners
See efficacy defined for kids
Examples of EFFICACY
- <questioned the efficacy of the alarms in actually preventing auto theft>
- In the planner's view, Rumsfeld had two goals: to demonstrate the efficacy of precision bombing and to “do the war on the cheap.” —Seymour M. Hersh, New Yorker, 7 Apr. 2003
- Vaccines exist, but their efficacy against aerosolized plague is unknown. —Sharon Begley et al., Newsweek, 8 Oct. 2001
- … efficacy does not have to be demonstrated before homeopathic products are marketed. —Alison Abbott et al., Nature, 26 Sept. 1996
- [+]more
Origin of EFFICACY
(see efficacious)
Related to EFFICACY
- Synonyms
- edge, effectiveness, effectualness, efficaciousness, efficacity, efficiency, productiveness
- Antonyms
- ineffectiveness, ineffectuality, ineffectualness, inefficiency
Learn More About EFFICACY
Browse
Next Word in the Dictionary: efficiencePrevious Word in the Dictionary: efficacityAll Words Near: efficacy
Seen & Heard
What made you want to look up efficacy? Please tell us where you read or heard it (including the quote, if possible).