What is the difference between pantyhose and tights? Well, in the U.S, it's the difference in the weight and opacity of the yarn (called the denier). Hosiery up to 40 denier are called "pantyhose" and anything thicker are called "tights." Pantyhose with a denier of 5 are very sheer (mostly see through and very light weight), whereas a 100 denier tight is opaque and doesn't let any light through to the skin. In the U.K., there are no "pantyhose"; they call them all "tights."