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 Hope Florida Foundation got a new board and filed tax returns, but criticisms of its efficacy still dog its leaders. — Christopher Spata, Miami Herald, 17 Oct. 2026 In oncology, where treatment efficacy hinges on precise, patient‑specific data, even a small AI hallucination, such as a mistimed test, can misdirect care. — Brad Kreick, Forbes.com, 16 Oct. 2026 That is the window in which the field’s claims about fewer side effects, meaningful efficacy at low circulating doses and consistent oral absorption either hold up or don’t. — Samantha Agate, Kansas City Star, 16 Oct. 2026 Bloomberg reports that insiders say Gemini 4 has solid model efficacy, but isn’t as stellar when employees actually use it, and that the model has issues with some coding tasks. — John Kell, Fortune, 7 Oct. 2026 See All Example Sentences for efficacy

Recent Examples of Synonyms for efficacy

Noun

The idea would be to equip all parties, from payers to providers to patients, with insights into effectiveness, cost, and value.

— Dana P. Goldman, STAT, 22 Oct. 2026
Other topical treatments—such as retinoids, peptides, and vitamin C—are backed by years of research on safety and effectiveness.

— Ashley Abramson, Allure, 22 Oct. 2026

Definition of effectiveness

Noun

Technique works well in testing This strategy optimizes both the transport and perovskite layers together, driving efficiency and durability to record levels.

— Mrigakshi Dixit, Interesting Engineering, 26 Oct. 2026
The longer-term outcome of the new approach, the agency hopes, will reduce the financial and technical burden on competing research teams and ultimately get missions from idea to orbit with efficiency and speed.

— Josh Dinner, Space.com, 26 Oct. 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 27 Oct. 2026.

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Synonyms of efficacy

noun

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