EFFICACY Synonyms: 22 Similar and Opposite Words

efficacy

noun

ˈe-fi-kə-sē

Definition of efficacy next

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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Example Sentences

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 The formula’s efficacy comes from its silicone-forward ingredient list (yes, silicones—which are a good thing, according to the Abbey Yung hair method and a lot of professional hair stylists) which makes hair silky smooth and shiny and protects it from damage. —

Gina Vaynshteyn, StyleCaster, 11 May 2026 While the concept of a token (as a unit or AI design) is common, even technological developments will change the connection between tokens and efficacy. —

Nisha Talagala, Forbes.com, 9 May 2026 The Resist Super Antioxidant Concentrate Serum pairs tetrahexyldecyl ascorbate with magnesium ascorbyl phosphate for a more stable, multi-angle approach to brightening, then layers in ferulic acid and vitamin E to boost efficacy. —

Christa Joanna Lee, Allure, 8 May 2026 After reports that vitamin K deficiency bleeding was on the rise, the American Academy of Pediatrics updated its policy statement in 2022 to stress the shot’s safety and efficacy. —

Duaa Eldeib, CNN Money, 8 May 2026 See All Example Sentences for efficacy

Recent Examples of Synonyms for efficacy

Noun

However, the study didn’t compare gadusol’s effectiveness to currently available sunscreens.

— Devika Rao, TheWeek, 18 May 2026
Instead, the court ruled that the effectiveness of Missouri’s map was in the hands of Hoskins, the secretary of state, who has the power to decide whether to certify the referendum for the ballot.

— Kacen Bayless, Kansas City Star, 18 May 2026