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 However, as the industry innovates with newer products such as high alcohol content beer or ready-to-drink cocktails, the efficacy of the categorical system continues to break down. — Adam Hoffer, Chicago Tribune, 5 July 2026 Harvard Health has taken a critical look at Apollo Neuro, and Medscape has warned about uncertain efficacy in at-home vagus stimulation devices. — Samantha Agate, Charlotte Observer, 3 July 2026 Harvard Health has published a critical take on Apollo Neuro, and Medscape has cautioned about at-home vagus nerve stimulation devices, warning of uncertain efficacy and safety. — Samantha Agate, Kansas City Star, 2 July 2026 Fifty years ago, the nation celebrated the 200th anniversary of its Declaration of Independence amid an outburst of patriotism and good feeling after surviving the 20th Century’s greatest threat to the efficacy of its democratic institutions. — Carl Leubsdorf, Mercury News, 4 July 2026 See All Example Sentences for efficacy

Recent Examples of Synonyms for efficacy

Noun

Mathematically, if quality is seven and acceptance is four, effectiveness is 28.

— Thomas Lim, Forbes.com, 2 July 2026
For Tokyo, that complicates the effectiveness of any unilateral intervention.

— Lee Ying Shan, CNBC, 1 July 2026

Definition of effectiveness

Noun

That was no more evident than when Kansas jumped from 104th in yards per play to 5th, and from 91st to 5th in passing efficiency.

— Shreyas Laddha, Kansas City Star, 6 July 2026
Prioritize efficiency, unleash thermal recovery and accelerate smarter system design.

— Kathleen “Katie” McGinty, Fortune, 6 July 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 7 Jul. 2026.

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Synonyms of efficacy

noun

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