Nylon is one of the most common polymers used as a fiber. Nylon is a thermoplastic silky material, first used commercially in a nylon-bristled toothbrush, followed more famously by women's "nylons" stockings. Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World War II. It replaced silk in military applications such as parachutes, flak vests, and was used in many types of vehicle tires.

It is round, smooth and shiny fiber. It has greater elasticity, high elongation. It has the ability to be lustrous, semi lustrous or dull. It is a strong thread when it comes to durability.

Nylon thread maintains a smooth, knot-free surface and is stronger than thread made from either cotton or linen. It has the advantage of being relatively inexpensive and can be manufactured in finer grades so that books sewn with it can be more easily nipped, rounded, and backed. Its principal disadvantages seem to be that it may cut the paper if the diameter of the thread is very small, and it has a tendency to contract upon release, so that when a group of sewn books is cut apart the nylon thread tends to contract and loosen the end sections.