Efficacy is the capacity to produce an effect. It has different specific meanings in different fields. In medicine, it is the ability of an intervention or drug to reproduce a desired effect in expert hands and under ideal circumstances.
Famous quotes containing the word efficacy:
“For books are not absolutely dead things, but do contain a potency of life in them to be as active as that soul was whose progeny they are; nay, they do preserve as in a vial the purest efficacy and extraction of that living intellect that bred them. I know they are as lively, and as vigorously productive, as those fabulous dragon’s teeth; and being sown up and down, may chance to spring up armed men.”
—John Milton (1608–1674)
“If there is a case for mental events and mental states, it must be that the positing of them, like the positing of molecules, has some indirect systematic efficacy in the development of theory.”
—Willard Van Orman Quine (b. 1908)