equivalent weight [L, a + aequus + valere, equal value; AS, gewiht] , 1. the weight of an element in any given unit (such as grams) that will displace a unit weight of hydrogen from a compound or combine with or replace a unit weight of hydrogen. 2. the weight of an acid or base that will produce or react with 1.008 grams of hydrogen ion. 3. the weight of an oxidizing or reducing agent that will produce or accept one electron in a chemical reaction.