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, effective delivery remains a critical challenge; Junho Jung stresses that topical applications often lack the efficacy of clinical injections, as ingredient stability and form are crucial for skin absorption. — Laia Farran Graves, Forbes.com, 12 Aug. 2026 Even before Bridge, the introduction of the current generation of GLP-1 medications for weight loss has brought prescribing challenges as profound as the medications’ remarkable efficacy. — Jeffrey Millstein, STAT, 11 Aug. 2026 The Japanese yen has already erased half the gains that came from the historic US-Japan currency intervention, raising questions over the efficacy of the maneuver and whether more currency moves may be needed to stop the yen’s slide. — Shelly Banjo, semafor.com, 10 Aug. 2026 But without a significant body of research proving these tools’ efficacy – and some studies showing harm – a growing number of experts are worried that children have become the guinea pigs of the next Big Tech experiment. — Aaron Glantz, Christian Science Monitor, 7 Aug. 2026 See All Example Sentences for efficacy

Recent Examples of Synonyms for efficacy

Noun

How closely matched the flu vaccine is to the dominant strain of the season is part of what accounts for the year-to-year changes in the shot’s effectiveness.

— Elise Haulund, CNN Money, 14 Aug. 2026
Because supplements don't have to undergo FDA approval for safety or effectiveness before being sold, Wood also recommends looking for products independently tested by a reputable third party.

— Dr. Onaola Adedeji, ABC News, 13 Aug. 2026

Definition of effectiveness

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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 17 Aug. 2026.

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Synonyms of efficacy

noun

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