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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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
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
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While Jaquez did not provide the eye-popping scoring of some of her teammates, the wing brought a cool effectiveness to the defensive side of the ball while tallying a pair of assists and a handful of deflections.—
Julia Poe,
Chicago Tribune,
10 May 2026
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The United States and Israel pounded Iran with devastating effectiveness for 37 days, killing much of the country’s leadership and destroying the bulk of its military, yet couldn’t collapse the regime or exact even the smallest concession from it.—
Robert Kagan,
The Atlantic,
10 May 2026
Noun
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Brown is still building up his pitch count with his transition from the bullpen to the rotation, requiring high efficiency facing Major League Baseball’s best offense to give them that many outs.—
Meghan Montemurro,
Chicago Tribune,
15 May 2026
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Goldman Sachs analysts reported in late 2025 that companies announcing layoffs carried higher debt, higher capital expenditure, and lower profit growth than peers, suggesting the cuts were responses to financial distress rather than AI efficiency gains.—
Julie Averill,
Forbes.com,
15 May 2026
Cite this Entry
“Efficacy.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/efficacy. Accessed 17 May. 2026.
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