The word polymer comes from the Greek "poly" meaning many, and "meros," parts or units. A polymer is a group of many units. You combine many
monomers (one unit) to create a polymer.
Polymer is often used as a synonym for "plastic," but many biological and inorganic molecules are also polymeric. All plastics are polymers, but not all polymers are plastics. Plastic actually refers to the way a material melts and flows.
Commercial polymers are formed through chemical reactions in large vessels under heat and pressure. Other ingredients are added to control how the polymer is formed and to produce the proper molecular length and desired properties. This chemical process is called "polymerization."
A homopolymer results from polymerizing only one kind of monomer. A copolymer results from using different monomers. Homopolymers have the same repeating unit while copolymers (which can be random, block, or graft) can vary have different numbers of repeating units. A terpolymer results from using three different monomers.