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

Bloomberg reports that insiders say Gemini 4 has solid model efficacy, but isn’t as stellar when employees actually use it, and that the model has issues with some coding tasks. — John Kell, Fortune, 7 Oct. 2026

Why the burning sensation is not a benefit That sharp alcohol sting many of us learned to equate with efficacy is doing no useful work. — Hanna Wickes, Sacbee.com, 5 Oct. 2026

Immunity from flu vaccination is generally thought to last for around four to six months before losing some efficacy, according to the CDC. — Stephen Underwood, Hartford Courant, 2 Oct. 2026

In early September, there was a virtual call with 80-plus artists, executives and stakeholders from the Asian music community with trustees and governors from the Recording Academy to review the efficacy of the new award. — Hannah Dailey, Billboard, 2 Oct. 2026