Efficacy - Wikipedia Efficacy is the ability to perform a task to a satisfactory or expected degree The word comes from the same roots as effectiveness, and it has often been used synonymously, although in pharmacology a distinction is now often made between efficacy and effectiveness
Efficacy - Word Genius “Efficacy” is easily confused with “efficiency,” but the meanings of the two words come from different Latin roots “Efficacy,” like “effectiveness,” describes a capacity for achievement
efficacy - Wiktionary, the free dictionary Efficacy refers to the beneficial effects of a program or policy under optimal conditions of delivery, whereas effectiveness refers to effects of a program or policy under more real-world conditions