Tights are a kind of cloth garment, most often sheathing the body from the waist to the toe tips with a tight fit, hence the name. They come in absolute opaque, opaque, sheer and fishnet styles — or a combination, such as the original concept of the American term pantyhose with sheer legs and opaque panty.
When made of fine silk, this hosiery was considered to be a stocking. When nylon fibers were developed and introduced in the 1940s, these stockings were referred to as nylons. When the separate legs were woven together with a panty that covered the lower torso up to the waist in a single, integrated format, the term pantyhose was coined, since it was a one piece construction of a panty with a pair of separate hose, one for each leg. This joining together eliminated any need for garters for holding up each separate leg covering.
In American English, the difference between pantyhose and tights is determined in the weight of the yarn used and the density or tightness of weaving to which the garment is knitted. Generally, anything up to forty denier in the leg or overall is known as pantyhose and anything over that can be classified as tights, as for example 'running tights' and 'cycling tights'. Tights can be sheer yet solid in colour, whereas leggings are practically or absolutely opaque, not sheer. Thus, the almost-opaque tights are sometimes labelled as semi-opaque and are not considered suitable as pants due to being too revealing or immodest. In the United Kingdom, the word "tights" is used for footed garments, which would always be worn under another item of clothing such as shorts or a skirt, while "leggings" refers to footless leg-wear of any denier, the exception being ballet tights which may have an opening under the sole allowing them to be rolled up to expose the foot without removing the garment. The word 'pantyhose' is not used in British English.
There are many sub-classifications of tights or pantyhose that describe the precise construction (such as control top, seamless, support and sheer).