What is the X in X-mas?
monovalent mon·o·va·lent (mŏn'ə-vā'lənt)
Able to form only one covalent or ionic bond.
Having a valence of one; univalent.
Of or relating to an antiserum containing an antibody or antibodies specific for one antigen.
Containing antigens from a single strain of a microorganism.
Having only one site of attachment. Used of an antibody or antigen.