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efficacy

noun
ef·​fi·​ca·​cy | \ ˈe-fi-kə-sē How to pronounce efficacy (audio) \
plural efficacies

Definition of efficacy

: the power to produce an effect
Synonyms & Antonyms Example Sentences Learn More about efficacy

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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
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Recent Examples on the Web

 The worrying fall coincides with the growth in the anti-vaxxer movement, with some parents expressing skepticism about the safety and efficacy of childhood vaccines. — Lianne Kolirin, CNN, "Vets fear anti-vax pet owners are putting their animals' health at risk," 5 Sep. 2019 The next study is expected to verify efficacy in humans by measuring the drug’s ability to decrease the number and size of polyps over a 12-month course of treatment. — Laura Garcia, ExpressNews.com, "Texas’ cancer-fighting agency invests millions in San Antonio research," 30 Aug. 2019 There's a lot of debate about the efficacy of state incentive programs though. — Bryn Elise Sandberg, The Hollywood Reporter, "California's New Film Czar on Boosting Tax Incentives, Obamas' Netflix Plans," 7 Aug. 2019 The 70-patient trial assessing safety and efficacy will be held at as many as 10 kidney centers in the U.S. The Rogosin Institute, a kidney-treatment center in New York, will be the initial trial site, CVS said. — Bloomberg News, al.com, "CVS looks to enter home dialysis business with help from Segway," 17 July 2019 Regions that have reckoned with infectious diseases on a widescale, including Rwanda and Bangladesh, were much more likely to believe in the safety and efficacy of vaccines. — Sy Mukherjee, Fortune, "Google, Pharma Giant Sanofi Team Up to Discover Drugs: Brainstorm Health," 19 June 2019 Today’s edition explores shifting attitudes on gun control, the human toll of climate change, a rare moment of unity in Brazil around pension reform, the efficacy of busing in education, and the thorny nature of emotional support animals. — The Christian Science Monitor, "Climate gloom and innovation bloom," 8 Aug. 2019 But ViiV injectables are the only long-acting ARVs likely to come to market anytime soon; the new Merck compound must still pass through large-scale efficacy trials. — Jon Cohen, Science | AAAS, "Simpler HIV treatment and prevention strategies take center stage," 24 July 2019 There are different efficacy rates for all of them. — Phil Rockrohr, chicagotribune.com, "Shout Out: Gretchen Waitley, a Vernon Hills resident with multiple sclerosis and organizer of PuckMS fundraiser," 19 July 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'efficacy.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of efficacy

13th century, in the meaning defined above

History and Etymology for efficacy

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

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More Definitions for efficacy

efficacy

noun
How to pronounce efficacy (audio)

English Language Learners Definition of efficacy

formal : the power to produce a desired result or effect

See the full definition for efficacy in the English Language Learners Dictionary

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