polymer

Very long-chain molecule made up of many repeated simple units (monomers) linked together by polymerization. There are many polymers, both natural (cellulose, chitin, lignin, rubber) and synthetic (polyethylene and nylon, types of plastic). Synthetic polymers belong to two groups: thermosoftening and thermosetting (see plastic).

The size of the polymer matrix is determined by the amount of monomer used; it therefore does not form a molecule of constant molecular size or mass. However, some biological polymers like proteins and DNA tend to have well-defined shapes and sizes.