Answer: Textiles

Even if you’ve never worked in the textile industry, if you’ve ever gone shopping for pantyhose or tights, then you’ve likely come across the term “denier” (pronounced like “den-yer”). Hose and tights are often labeled with a number and the word or simply “Den” or a “D”, like 120 Denier or 80 D.

The term is a unit of measure indicating the linear mass density of fibers with one denier equivalent to one gram of mass per 9000 meters of fiber. Why 9000 meters? The origin of the measurement comes from measuring silk and it takes 9000 meters of silk to reach 1 gram of mass. The origin of the term is a cross application of the French denier, a low value coin (if the textile term had originated in Britain or the United States, then perhaps the textile term would be penny instead of denier).

The lower the denier count, the thinner and more gossamer like the material. A pair of hose with a 5 D rating are incredibly lightweight. A pair of hose with a 70+ rating are usually woven densely enough to be opaque. By the time you get into 150+ denier ratings, you’re approaching a thickness and weight you might more closely associate with leggings than pantyhose.