Home › Words › E › efficaciousnessefficaciousnessefficaciousness means quality of being efficacious.EtymologyFrom efficacious + -ness.nounQuality of being efficacious.e.g.“In ancient mythology, the efficaciousness of the satyrion is attested, particularly in the case of Hercules.” — 1961, Harry E. Wedeck, Dictionary of Aphrodisiacs, New York: The Citadel Press, page 216:Definitions & examples from Wiktionary (CC BY-SA 3.0).Words closest in meaningBy meaning, not spelling — each word's AI semantic fingerprint, nearest first.efficacious 85% match — Effective; possessing efficacy. vs efficaciousness →effectuousness 85% match — Quality of being effectuous. vs efficaciousness →efficacity 79% match — Efficacy. vs efficaciousness →effectualness 78% match — The state or condition of being effectual. vs efficaciousness →efficious 78% match — Efficacious. vs efficaciousness →effectuality 76% match — The state or condition of being effectual. vs efficaciousness →inefficaciousness 75% match — Lack of efficacy. vs efficaciousness →effectuous 75% match — Effective; efficacious. vs efficaciousness →