The monomer of polythene is ethylene. Monomer 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 complexPolyethylene or polyethene is the most common plastic. The annual global production is approximately 80 million tonnes. Its primary use is in packaging. Ethylene is a hydrocarbon which has the formula C 2H 4 or H2C=CH2. It is a colorless flammable gas with a faint “sweet and musky” odor when pure. It is the simplest alkene, and the second simplest unsaturated hydrocarbon after acetylene.