Definition of efficacy in English:



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


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