A monomer (/ˈmɒnəmər/ MON-ə-mər) (mono-, "one" + -mer, "part") is a molecule that may bind chemically to other molecules to form a polymer. The term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex. The most common natural monomer is glucose, which is linked by glycosidic bonds into polymers such as cellulose and starch, and is over 77% of the mass of all plant matter. Most often the term monomer refers to the organic molecules which form synthetic polymers, such as, for example, vinyl chloride, which is used to produce the polymer polyvinyl chloride (PVC).The process by which monomers combine end to end to form a polymer is called polymerization. Molecules made of a small number of monomer units, up to a few dozen, are called oligomers.Monomer: A substance composed of monomer molecules.Monomer molecule: A molecule which can undergo polymerization, thereby contributing constitutional units to the essential structure of a macromolecule.