efficacy

noun

ef·​fi·​ca·​cy ˈe-fi-kə-sē How to pronounce efficacy (audio)
plural efficacies
: the power to produce an effect

Examples of efficacy in a Sentence

In the planner's view, Rumsfeld had two goals: to demonstrate the efficacy of precision bombing and to "do the war on the cheap." Seymour M. Hersh, New Yorker, 7 Apr. 2003
Vaccines exist, but their efficacy against aerosolized plague is unknown. Sharon Begley et al., Newsweek, 8 Oct. 2001
efficacy does not have to be demonstrated before homeopathic products are marketed. Alison Abbott et al., Nature, 26 Sept. 1996
questioned the efficacy of the alarms in actually preventing auto theft
Recent Examples on the Web The initial mistake launched an initiative that substantially enhanced our overall efficacy and communication data. Frayda Leibtag, Forbes, 29 Feb. 2024 Designing new molecular mechanisms from scratch, in her view, can produce better efficacy. Matthew Herper, STAT, 29 Feb. 2024 This deodorant earned top marks for its efficacy against sweat and odor. Katrina Cossey, Parents, 22 Feb. 2024 While its actual efficacy is still widely debated, AA is still a star in the entertainment world. Laura Bratton, Quartz, 21 Feb. 2024 So when shopping for hair masks and conditioners that promote hair growth, a lot goes into determining their overall efficacy. Jessie Quinn, Peoplemag, 13 Feb. 2024 Cowen said that even without such a framework, potentially life-saving antifungals shouldn’t be dropped because of the risks the new fungicides pose to the antifungals’ efficacy. Kaitlin Sullivan, NBC News, 11 Feb. 2024 The agency approved the drug based on safety and efficacy data from the Phase 3 OUtMATCH study, which evaluated the medication in 168 patients aged 1 to 55 with allergies to peanuts and at least two other foods, including milk, wheat and cashews. Cailey Gleeson, Forbes, 16 Feb. 2024 Kratom has not been evaluated by the FDA for safety or efficacy. Sponsored Content, The Mercury News, 16 Feb. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'efficacy.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

borrowed from Latin efficācia, from efficāc-, efficāx "capable of fulfilling a function, efficacious" + -ia -y entry 2

First Known Use

13th century, in the meaning defined above

Time Traveler
The first known use of efficacy was in the 13th century

Dictionary Entries Near efficacy

Cite this Entry

“Efficacy.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/efficacy. Accessed 18 Mar. 2024.

Kids Definition

efficacy

noun
ef·​fi·​ca·​cy ˈef-i-kə-sē How to pronounce efficacy (audio)
plural efficacies
: the power to produce a desired result

More from Merriam-Webster on efficacy

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