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
Homan, who is widely associated with immigration enforcement actions that separated families, was given a Presidential Rank Award by the Obama administration to tout his efficacy in 2015.
—
Safiyah Riddle, Fortune, 26 Jan. 2026
Along with the changes to vaccine exemptions, Yarborough’s bill would require anyone providing a child with a vaccine to tell their parents the risks, benefits, safety and efficacy of the vaccine.
—Romy Ellenbogen, Miami Herald, 26 Jan. 2026
Isaacson noted there are decades of research on the efficacy of vaccinations, but things started to change with the COVID-19 pandemic.
—Mike Danahey, Chicago Tribune, 24 Jan. 2026
But environmental experts question the efficacy of the Environmental Protection Agency’s testing approach, which does not align with the standards used after past California wildfires.
—James Rainey, Los Angeles Times, 13 Jan. 2026
See All Example Sentences for efficacy
Safiyah Riddle, Fortune, 26 Jan. 2026
Along with the changes to vaccine exemptions, Yarborough’s bill would require anyone providing a child with a vaccine to tell their parents the risks, benefits, safety and efficacy of the vaccine.
—Romy Ellenbogen, Miami Herald, 26 Jan. 2026
Isaacson noted there are decades of research on the efficacy of vaccinations, but things started to change with the COVID-19 pandemic.
—Mike Danahey, Chicago Tribune, 24 Jan. 2026
But environmental experts question the efficacy of the Environmental Protection Agency’s testing approach, which does not align with the standards used after past California wildfires.
—James Rainey, Los Angeles Times, 13 Jan. 2026
See All Example Sentences for efficacy
Recent Examples of Synonyms for efficacy
Noun
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The state spent more than $20 billion without uniform standards to measure effectiveness.—
Julie Watts,
CBS News,
27 Jan. 2026
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Demonstrating the effectiveness of their tactical setup without the ball, Villa have only made more interceptions and ball recoveries in one other match this season.—
Jacob Tanswell,
New York Times,
26 Jan. 2026
Noun
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For 2026, the current-generation Prius returns with the same basic formula — excellent efficiency — wrapped in a design that’s finally not so frumpy.—
Brian Moody,
AJC.com,
30 Jan. 2026
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Big names like Washington’s Bobby Wagner, New Orleans’ Demario Davis, Green Bay’s Quay Walker and Cleveland’s Devin Bush are durable, effective leaders in the middle who would provide day one efficiency.—
Nick Harris,
Fort Worth Star-Telegram,
30 Jan. 2026
Cite this Entry
“Efficacy.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/efficacy. Accessed 1 Feb. 2026.
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