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

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

The protection lasts up to six washes and doesn’t degrade or lose efficacy from sweat or UV exposure. — Maggie Slepian, Travel + Leisure, 23 July 2026

Scientists say that raises some big concerns about safety and efficacy. — Sarah Boden, NPR, 22 July 2026

That study, which tests for safety and determines the most effective and tolerable size of a dose, is needed before the vaccine can be tested in the field in a larger efficacy trial. — Helen Branswell, STAT, 22 July 2026