A monomer is a single atom or molecule which is able to join with other monomers to make new substances called polymers. The words come from the Greek language where "mono" means "one", "poly" means "many", and "meros" means "a part". A feature of monomers is that they have two carbon atoms which are joined, called a carbon double bond. The double bond allows the monomer to make the long chains of polymers. There are thousands of different monomers. Examples of monomers include monosaccharide which is simple sugar, glycerol, amino acid and nucleotide. The most made monomer is ethylene