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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).

Definition of efficacy in:
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