EFFICACY Synonyms: 22 Similar and Opposite Words

efficacy

noun

ˈe-fi-kə-sē

Definition of efficacy

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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Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.

Recent Examples of efficacy Kennedy has a history of casting doubts on vaccines and spreading misleading claims about their safety and efficacy. — Stephanie Stahl, CBS News, 27 Aug. 2026 Without needing to establish safety or efficacy, researchers can skip ahead to trials testing their broader potential. — Mike McRae 26, New Atlas, 26 Aug. 2026 But over time, people’s loyalty to online brands may be supplanted by the efficacy of their interfaces for agents. — George C. Lee Ii, Fortune, 26 Aug. 2026 Ongoing trials, for example, are studying the efficacy of B7-H3 as a target for antibody-drug conjugates, a cancer treatment in which antibodies bind to proteins on cancer cells to more directly deliver chemotherapy drugs. — Isabella Backman, Hartford Courant, 24 Aug. 2026 See All Example Sentences for efficacy

Recent Examples of Synonyms for efficacy

Noun

Implement a digital visual-management platform across six facilities to standardize workflows and improve infection prevention, care coordination, workforce effectiveness, quality, and patient safety.

— Arkansas Democrat-Gazette, Arkansas Online, 27 Aug. 2026
Apart from the penalty, Meta agreed as part of the settlement to algorithmic changes that could dampen engagement and the effectiveness of its advertising, dampening investor sentiment toward the resolution of the case.

— Tobias Burns, CNBC, 26 Aug. 2026

Definition of effectiveness

Noun

The balance between efficiency and pleasantness in doing business seems extremely hard to achieve.

— Judith Martin, Mercury News, 25 Aug. 2026
Big banks—including JPMorgan, Citi, Wells Fargo, and Bank of America—are all investing heavily in AI to boost efficiency, and Bank of America is already pointing to measurable returns.

— Sheryl Estrada, Fortune, 24 Aug. 2026

Definition of efficiency

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efficacity

efficacy

efficiency

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“Efficacy.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/efficacy. Accessed 1 Sep. 2026.

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Synonyms of efficacy

noun

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