efficacy
nounOPAL W
/ˈefɪkəsi/
/ˈefɪkəsi/
[uncountable] (formal)- the ability of something to produce the results that are wanted synonym effectiveness
- to evaluate the efficacy and safety of the treatment
Word Originearly 16th cent.: from Latin efficacia, from efficax, efficac-, from efficere ‘accomplish’, from ex- ‘out, thoroughly’ + facere ‘do, make’.