Tights are a kind of cloth leg garment, most often sheathing the body from about the waist to the feet with a more or less tight fit, hence the name.
Wearing of tights has a long history going back several centuries, when they were worn by men. Today, they are worn primarily by women and girls and some men and boys, as well as infants and toddlers of both sexes. In recent years, they have been sometimes offered as men's fashion. Athletic tights are already considered unisex.
In American English, the difference between pantyhose and tights is determined in the weight of the yarn used and the thickness to which the garment is knitted. Generally, anything up to 40 denier is known as pantyhose and anything over can be classified as tights. In the United Kingdom, the word "tights" is used in all cases when referring to pantyhose.
There are many sub-classifications of tights/pantyhose that describe the precise construction (such as control top, seamless, support). Although most tights are mainly nylon or cotton, lycra is normally included in modern blends to improve fit.
Unfooted tights are usually called leggings. Athletic tights are often unfooted, although they may have a "stirrup" that goes under the foot to hold the cuff down near the ankle.