Synonyms of efficacy

efficacy

noun

ˈe-fi-kə-sē 

as in effectiveness

the power to produce a desired result

questioned the efficacy of the alarms in actually preventing auto theft

Synonyms & Similar Words

• effectiveness
• efficaciousness
• efficiency
• productiveness
• ability
• efficacity
• effectualness
• capability
• edge
• strength
• potency
• capacity
• puissance

Antonyms & Near Antonyms

• ineffectiveness
• inefficiency
• inability
• inadequacy
• ineffectuality
• ineffectualness
• incompetence
• incompetency
• inadequateness

Example Sentences

Recent Examples of efficacy

The efficacy of Stones’ skill set was brought into sharper focus during that treble-winning season in 2022-23. — Mark Carey, New York Times, 26 July 2026

Recently, Overton has been involved in drafting new policies for the use of peptides, short chains of amino acids that are available on the gray market but that, in many cases, have scant scientific evidence to support their safety or efficacy. — Michael Scherer, The Atlantic, 24 July 2026

The current study was designed to evaluate the clinical efficacy of fecal transplant, not to establish the precise biological mechanism, Wang and Bao say. — Erica Sweeney, EverydayHealth.com, 24 July 2026

At the time, the FDA cited safety concerns and a lack of evidence supporting their efficacy. — Maggie Ryan, Flow Space, 24 July 2026