efficacy
Pronunciation
Noun
C1 Advanced
Quick answer
The ability of something to produce the intended result.
Synonyms and antonyms
Synonyms
effectiveness
Antonyms
ineffectiveness
Usage notes
More formal than "effectiveness" and common in medical or scientific writing.
Test yourself
Which word fits the gap? "The trial tested the _____ of the new vaccine."
Answer: efficacy
In your own words, what does "efficacy" mean?
The ability of something to produce the intended result.
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