Polymers are “chemical compounds or mixture of compounds formed by polymerization and consisting of repeat structural units (monomers).”  Webster’s dictionary p. 658. Monomers – structural repeat units of polymer that are connected to each other by covalent bonds.

Example: Polyethylene

Example: DNA molecule

Degree of polymerization N – number of monomers in a polymer molecule.
For typical synthetic polymers:  N ~
Natural polymers - DNA molecules: N ~