According to About.com, denier is not a type of nylon but a measure of the fineness of the fiber. One denier is equal to 1 gram per 9,000 meters of yarn. Manufacturers use the term "denier" with both natural and man-made fibers.
A number normally precedes the word "denier." For example, 2,500-denier ballistic nylon is the type that manufacturers use in making high-end luggage that is smooth and lint-resistant. Lower-quality luggage manufacturers often choose less expensive 600- to 1,800-denier polyester, which costs less but does not provide the durability of the more expensive product.
As first synthetic fabric as developed by DuPont, nylon remains one of the company's most successful products. While the DuPont is responsible for the name, it is not a registered trademark. This decision is responsible for the word becoming synonymous with stockings.
Nylon has many commercial uses other than hosiery. In the automotive industry, nylon fibers form the cords that provide strength for tires. DuPont's willingness to stop nylon hose production during World War II and only a few years after their introduction and the company's work with the military continues to provide benefits as it develops uses for the material. DuPont's newer formulations allow production of items other than fabric, including gears, ball bearings, cams and valves to replace metal parts while reducing weight.