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

That vote was based on its superior efficacy to existing seasonal flu shots and a good safety record demonstrated in trials that included nearly 44,000 people. — Beth Mole, ArsTechnica, 6 Aug. 2026

And with that practice come new, more advanced discussions about the safety, efficacy and depth of this technology in our workplaces. — Larry Bradley, Forbes.com, 6 Aug. 2026

The drug has also shown higher efficacy than a rival obesity pill from Lilly, which launched a few months later than Novo's treatment. — Annika Kim Constantino, CNBC, 6 Aug. 2026

How much efficacy can that kind of humanization have when faced with the naked desire for power, for resources, for land, for geopolitical advantage? — Orna Guralnik, The New York Review of Books, 4 Aug. 2026