n. The condition of being equivalent; equality in value; correspondence in signification, force, nature, or the like: as, a universal equivalence of weights and measures is extremely desirable; exact equivalence between different words is rare. Also equivalency.To be equivalent to; counterpoise.n. In chem., capability of mutual replacement, in chemical combination, of definite quantities of different substances: thus, there is equivalence between approximately 18.07 parts of aluminium, 40.1 of calcium, 46.1 of sodium, and 55.9 of (ferrous) iron in combining with the same fixed quantity of oxygen.