as in effectiveness
the power to produce a desired result
questioned the efficacy of the alarms in actually preventing auto theft
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Recent Examples of efficacy
Kennedy has in particular made skepticism toward antidepressants for adolescents a centerpiece of his public health agenda, even claiming that antidepressants may be harder to quit than heroin — a stance that ignores decades of evidence about their safety and efficacy.
—
Stephen B. Soumerai, STAT, 7 Jan. 2026
For both 10Beauty and Luum, the next few months are about ensuring efficacy and efficiency in service.
—Noor Lobad, Footwear News, 6 Jan. 2026
But Roethling says these products can spoil quickly and lose their efficacy when kept in an area with temperature and humidity fluctuations.
—Madeline Buiano, Martha Stewart, 4 Jan. 2026
At the highest dose, the drug showed 76% efficacy —surpassing the 60% threshold for herd immunity.
—Noelle Harff, San Diego Union-Tribune, 31 Dec. 2025
See All Example Sentences for efficacy
Stephen B. Soumerai, STAT, 7 Jan. 2026
For both 10Beauty and Luum, the next few months are about ensuring efficacy and efficiency in service.
—Noor Lobad, Footwear News, 6 Jan. 2026
But Roethling says these products can spoil quickly and lose their efficacy when kept in an area with temperature and humidity fluctuations.
—Madeline Buiano, Martha Stewart, 4 Jan. 2026
At the highest dose, the drug showed 76% efficacy —surpassing the 60% threshold for herd immunity.
—Noelle Harff, San Diego Union-Tribune, 31 Dec. 2025
See All Example Sentences for efficacy
Recent Examples of Synonyms for efficacy
Noun
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Each of these decisions moves the state further away from the clarity taxpayers, students and families need to evaluate the effectiveness of the system and the readiness of students.—
Bruce Rauner,
Chicago Tribune,
6 Jan. 2026
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Breeze head coach Noelle Quinn compared Bueckers’ effectiveness in Unrivaled’s 3-on-3 format to Skylar Diggins, pointing to how dangerous both players become when the floor opens up and decisions have to be made quickly.—
Miami Herald,
Miami Herald,
6 Jan. 2026
Noun
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The aim is to significantly increase the power density and efficiency of water electrolysis to produce green hydrogen based on noble metal-free catalysts in comparison to current systems.—
Prabhat Ranjan Mishra,
Interesting Engineering,
11 Jan. 2026
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Though designers will still prioritize efficiency, the triangle might not always be the default layout to achieve what a homeowner wants.—
Kristina McGuirk,
Better Homes & Gardens,
10 Jan. 2026
Cite this Entry
“Efficacy.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/efficacy. Accessed 11 Jan. 2026.
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