Efficacy is defined as the ability to do what is defined as desired or to be effective at producing a result.
The ratio of the energy delivered (or work done) by a machine to the energy needed (or work required) in operating the machine. The efficiency of any machine is always less than one due to forces such as friction that use up energy unproductively.
Intensity of emotion or belief:
Find another word for effectiveness. In this page you can discover 14 synonyms, antonyms, idiomatic expressions, and related words for effectiveness, like: ineffectiveness, uselessness, unproductivity, effect, effectuality, effectualness, efficaciousness, efficacy, efficiency, influence and potency.