When monomers join together they form a polymer. A monomer is a single unit that is repeated several times to form a long chain of units, or a large molecule referred to as a macromolecule. Polymers can be naturally occurring as well as synthetic.
The process of combining monomer units into large molecules is called polymerization. Polyvinyl chloride is an example of a synthetic plastic polymer in which the monomer unit is the vinyl chloride unit, or C2H3Cl. Polyethylene and polypropylene are some widely used synthetic polymers.
Wool, rubber, amber, cellulose and silk are examples of naturally occurring polymers. The genetic material DNA, found in the nucleus of a cell, is also a polymer.