efficacy

noun
ef·​fi·​ca·​cy | \ ˈe-fi-kə-sē \
plural efficacies

Definition of efficacy

: the power to produce an effect

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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

And while melatonin for the most part is okay for adults, the FDA does not regulate supplements for safety or efficacy. Caroline Picard, Good Housekeeping, "What You Need to Know About OTC Sleep Aids, According to Neurologists," 30 Jan. 2019 Medical trials have shown strong evidence for the efficacy of a vaccine from Merck & Co. Inc., which has begun the process of seeking approval from the Food and Drug Administration. Thomas M. Burton, WSJ, "U.S. Pulls Ebola Experts From Congo Combat Zones," 14 Nov. 2018 Global Science Research, that third party, were the ones who crafted the personality quiz for maximum efficacy, and actually did the data extraction. CBS News, "What you need to know about Facebook & Cambridge Analytica," 20 Mar. 2018 The standard for efficacy was clearing the fungus from the blood or other normally sterile parts of the body. Bradley J. Fikes, sandiegouniontribune.com, "Cidara's antifungal passes mid-stage human testing, but shares plummet," 19 Mar. 2018 If efficacy and odor tests pass, Degree might still decide to go back and look at a particular product’s formula to adjust ingredients and incorporate expert feedback. Cassie Shortsleeve, Popular Mechanics, "How Scientists at Degree Men Test Antiperspirant," 20 Dec. 2018 Four months of bedrest had left me with atrophied muscles and a body overloaded with ice cream, antibiotics, and painkillers—this would be great test of Espace Chenot’s efficacy. Irena Medavoy, Town & Country, "How to Detox Like a Hollywood Power Player," 5 Nov. 2018 Related Phase 1 studies typically look only at safety, while midstage Phase 2 trials look at efficacy. Joseph Walker, WSJ, "Biotechs With No Drugs in Trial Are Raising Millions in IPOs," 31 Oct. 2018 Especially since a review published in Pathobiology of Aging & Age-Related Diseases concluded that, while the current evidence on zinc's efficacy is limited, what is available looks promising. Amy Capetta, Woman's Day, "5 Anti-Aging Supplements That May Actually Work," 16 Oct. 2018

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, efficacikous" + -ia -y entry 2

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Statistics for efficacy

Last Updated

13 Feb 2019

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Time Traveler for efficacy

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

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More Definitions for efficacy

efficacy

noun

English Language Learners Definition of efficacy

formal : the power to produce a desired result or effect

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Comments on efficacy

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a servile follower or underling

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