the quality of being enduring and free from change or variation; "early mariners relied on the constancy of the trade winds"
faithfulness and dependability in personal attachments (especially sexual fidelity)
(psychology) the tendency for perceived objects to give rise to very similar perceptual experiences in spite of wide variations in the conditions of observation
marked by qualities giving the power to produce an intended effect; "written propaganda is less efficacious than the habits and prejudices...of the readers"-Aldous Huxley; "the medicine is efficacious in stopping a cough"