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Synonyms
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."
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Seymour M. Hersh, New Yorker, 7 Apr. 2003
Vaccines exist, but their efficacy against aerosolized plague is unknown.
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Sharon Begley et al., Newsweek, 8 Oct. 2001
… efficacy does not have to be demonstrated before homeopathic products are marketed.
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Alison Abbott et al., Nature, 26 Sept. 1996
questioned the efficacy of the alarms in actually preventing auto theft
Recent Examples on the Web
Some of the senators tried to show him data, referencing the deep scientific literature supporting the safety and efficacy of vaccines, including the Measles, Mumps, and Rubella Vaccine (MMR) and the HPV vaccine.
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Ars Technica, 31 Jan. 2025
Not to mention, research suggests there is no safety or efficacy benefit to getting the drug prescribed by a doctor in person (with testing, like an ultrasound) versus receiving it in the mail without any prior testing.
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Korin Miller, SELF, 29 Jan. 2025
This effectively meant the creatine doubled the efficacy of the psychotherapy, with 12 participants in the supplement group achieving full remission at the end of the eight weeks compared to just five in the placebo group.
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Rich Haridy, New Atlas, 29 Jan. 2025
As chairman of the nonprofit Children's Health Defense, he has been outspoken about the safety of vaccines, despite overwhelming scientific consensus supporting their efficacy.
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Jonathan Granoff, Newsweek, 29 Jan. 2025
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Word History
Etymology
borrowed from Latin efficācia, from efficāc-, efficāx "capable of fulfilling a function, efficacious" + -ia -y entry 2
First Known Use
1527, in the meaning defined above
Dictionary Entries Near efficacy
Cite this Entry
“Efficacy.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/efficacy. Accessed 12 Feb. 2025.
Kids Definition
More from Merriam-Webster on efficacy
Nglish: Translation of efficacy for Spanish Speakers
Britannica English: Translation of efficacy for Arabic Speakers
Britannica.com: Encyclopedia article about efficacy
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