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 drug’s lack of efficacy cannot be blamed on patients, said Alexander Miras, an obesity expert at Ulster University, to The Guardian. — Theara Coleman, TheWeek, 9 Sep. 2026

Critically, Pachocki wrote that one of the primary tools OpenAI and other AI companies have used to verify if AI models are following user intentions and check for misbehavior is losing its efficacy. — Jeremy Kahn, Fortune, 8 Sep. 2026

Clinical trials to test the drug’s efficacy yielded promising results in improving lung function and expansion, per Insilico. — Rachel Raposas, PEOPLE, 8 Sep. 2026

Lack of self-efficacy Lahey explains that kids who never have to deal with the consequences of their actions end up feeling a lack of self-efficacy. — Cheryl Maguire, Parents, 1 Sep. 2026