High molecular weight chemical com- pounds formed by repeated linking of smaller chemical units called monomers. Polymers from which fibres are made are long chain molecules in which the monomers are linked end to end linearly. Synthetic polymers used for carpet fibre include nylon-6, 6 and nylon-6 (polyamides), polyester, polypropylene, and polyacrylonitrile (acrylics). In popular terminology, polymers are also called plastics or resins.