Efficacy meaning:

efficacy meaning , definition , what is efficacy : the ability of something to produce the ...: Learn more. Efficacy is the quality of being successful in producing an intended result or effect. Learn how to use this word in different contexts, synonyms, and related terms with Collins English Dictionary. 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.