Share this entry

efficacy Line breaks: ef¦fi|cacy
Pronunciation: /ˈɛfɪkəsi/

Definition of efficacy in English:


[mass noun] formal
The ability to produce a desired or intended result: there is little information on the efficacy of this treatment
More example sentences
  • It'll be some time before the safety and efficacy of the other products is proven.
  • The power of transformation or efficacy of the commodity is often a selling point.
  • Blood tests may be needed periodically to monitor the treatment and its efficacy.


Early 16th century: from Latin efficacia, from efficax, efficac- (see efficacious).

Words that rhyme with efficacy

mendicancy • prolificacy

Definition of efficacy in:

Share this entry


What do you find interesting about this word or phrase?

Comments that don't adhere to our Community Guidelines may be moderated or removed.

Get more from Oxford Dictionaries

Subscribe to remove adverts and access premium resources

Word of the day haughty
Pronunciation: ˈhɔːti
arrogantly superior and disdainful