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. 2003Vaccines 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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But prorating three years of player profits down to 12 months, as UEFA’s rule does, reduces the immediate efficacy of successful trading in the market, the very strategy that poorer clubs increasingly rely on to climb the ladder.—Chris Weatherspoon, New York Times, 5 Sep. 2025 And no longevity-claiming therapy is considered fruitful without sound research that confirms efficacy after following a diverse cohort of humans for decades to see if the therapy is associated with extended life or staving off chronic disease.—Alexa Mikhail, Flow Space, 5 Sep. 2025 Thanks to its ease, efficacy, and film-free finish, Pavitt loves micellar water for acne-prone skin types.—Iman Balagam, Vogue, 3 Sep. 2025 In a makeup context, the question became how to preserve this full efficacy while also introducing color.—Celia Shatzman, Forbes.com, 3 Sep. 2025 See All Example Sentences for efficacy
Word History
Etymology
borrowed from Latin efficācia, from efficāc-, efficāx "capable of fulfilling a function, efficacious" + -ia-y entry 2
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