- capacity for producing a desired result or effect; effectiveness: a remedy of great efficacy.
Origin of efficacy
- the quality of being successful in producing an intended result; effectiveness
Word Origin and History for efficacies
1520s, from Latin efficacia "efficacy, efficiency," from efficax (genitive efficacis) "powerful, effective," from stem of efficere "work out, accomplish" (see effect). Earlier in same sense was efficace (c.1200), from Old French eficace (14c.), from Latin efficacia; also efficacite (early 15c.), from Latin efficacitatem.