Definition of efficacy in English:



mass nounformal
  • The ability to produce a desired or intended result.

    ‘there is little information on the efficacy of this treatment’
    • ‘However, there is very little evidence on the comparative efficacy of classes of drugs.’
    • ‘The partisanship has even reduced their efficacy as a binding force of our nation.’
    • ‘There was a lack of data on efficacy and adverse effects for all the other drugs.’
    • ‘Drugs with comparable efficacy but better safety profiles later appeared on the market.’
    • ‘The government claims this is part of a research project to test the safety and efficacy of the drug.’
    • ‘Blood tests may be needed periodically to monitor the treatment and its efficacy.’
    • ‘The power of transformation or efficacy of the commodity is often a selling point.’
    • ‘The sooner the morning after pill is taken after sex the greater its efficacy.’
    • ‘It has proved efficacy in the treatment of depression and has been shown to be cost effective.’
    • ‘In order to have any efficacy whatever, a world organization must be able to override big states as well as small ones.’
    • ‘On its own this finding is insufficient to define the relative efficacy of the two treatments.’
    • ‘Concerns about the safety and efficacy of human cloning, then, do not warrant a ban in law.’
    • ‘The report noted that it does not evaluate the actual efficacy of the programs themselves.’
    • ‘Clinical trials are in progress to assess its efficacy in severe asthma.’
    • ‘He argued that monitoring of treatment efficacy would be difficult and expensive.’
    • ‘The trials also showed that efficacy is sustained during a one-year treatment period.’
    • ‘They have had seven matches together, but judgment on their efficacy has been reserved.’
    • ‘Our aim was not to assess efficacy of antibiotics but the effectiveness of prescribing strategies.’
    • ‘It'll be some time before the safety and efficacy of the other products is proven.’
    • ‘Well, I don't have a huge list of examples but I've seen enough to convince me of it's efficacy.’
    success, successfulness, productiveness, fruitfulness, potency, power
    effectiveness, success, successfulness, productiveness, fruitfulness, potency, power
    View synonyms


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