Source : Webster's Revised Unabridged Dictionary (1913)

Multivalence \Mul*tiv"a*lence\, n. (Chem.)
   Quality, state, or degree, of a multivalent element, atom, or
   radical.

Source : WordNet®

multivalence
     n : the state of being polyvalent [syn: {polyvalence}, {polyvalency},
          {multivalency}]