Dictionary.net

1. The valence or combining power of a substance. 2. The number of hydroxyl groups contained in a base or an alcohol.

Combining capacity of an element, number of atoms of hydrogen with which one of its atoms normally combines.

Chemical valency or quantivalence.

Syn. : combining capacity quantivalence, valence, valency. The combining power of an element as compared with that of hydrogen; a number representing the greatest number of atoms of hydrogen which it will replace in a compound, or with which it is capable of combining, or twice the number of oxygen atoms with which one of its atoms can combine. The degrees of a. are expressed by the terms univalence, or the a. of a monad element, which replaces one atom of hydrogen; bivalence, or the a. of a diad element, replacing two atoms of hydrogen; trivalence, or the a. of a triad element; quadrivalence, or the a. of a tetrad element; quinquivalence, or the a. of a pentad element; sexvalence, or the a. of a hexad element; etc.