Source : Webster's Revised Unabridged Dictionary (1913)

Monovalent \Mo*nov"a*lent\, a. [Mono- + L. valens, p. pr. See
   {Valence}.] (Chem.)
   Having a valence of one; univalent. See {Univalent}.

Source : WordNet®

monovalent
     adj 1: containing only one kind of antibody [ant: {polyvalent}]
     2: having a valence of 1 [syn: {univalent}] [ant: {polyvalent}]