What does the word efficacy mean?

Usage examples for efficacy

  1. This is not to deny the reality of a power not ourselves making for health and well- being generally, or the power of faith, or the efficacy of prayer. – Modern Religious Cults and Movements by Gaius Glenn Atkins
  2. What was the nature and efficacy of their system of cross- examination, he knew; and he knew how nothing but ignorance could preserve poor Mars Plaisir from treachery. – The Hour and the Man An Historical Romance by Harriet Martineau
  3. From this trial of the efficacy of our means of security, it was plain that the Fury could not possibly be hove down under circumstances of such frequent and imminent risk: I therefore directed a fourth anchor, with two additional cables, to be carried out, with the hope of breaking some of the force of the ice by its offering a more oblique resistance than the other, and thus, by degrees, turning the direction of the pressure from the ships. – Three Voyages for the Discovery of a Northwest Passage from the Atlantic to the Pacific, and Narrative of an Attempt to Reach the North Pole, Volume 2 (of 2) by Sir William Edward Parry