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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The new report is the second in recent weeks to cast doubt on the efficacy of Meta’s child-safety tools.—Charlotte Alter, Time, 9 Oct. 2025 That's significantly better than the current efficacy of the drug, which typically takes three to six months to produce new hair growth in humans.—New Atlas, 8 Oct. 2025 The 10 dead roaches were a testament to the efficacy of the tracking power pesticide.—David J. Neal, Miami Herald, 7 Oct. 2025 According to the team, most of the new compounds previously studied for MASLD treatment have failed in clinical trials, for reasons including efficacy and safety.—Hannah Millington, MSNBC Newsweek, 6 Oct. 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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