Chemistry. the quality that determines the number of atoms or groups with which any single atom or group will unite chemically. the relative combining capacity of an atom or group compared with that of the standard hydrogen atom. The chloride ion, Cl–, with a valence of one, has the capacity to unite with one atom of hydrogen or its equivalent, as in HCl or NaCl.
Immunology. the number of determinants per molecule of antigen.
the capacity of one person or thing to react with or affect another in some special way, as by attraction or the facilitation of a function or activity.
a city in and the capital of Drôme, in SE France.
a department in SE France. 2533 sq. mi. (6560 sq. km). Capital: Valence.