Underwear, underclothing, or undergarments are items of clothing worn beneath outer clothes, usually in direct contact with the skin, although they may comprise more than a single layer. They serve to keep outer clothing from being soiled or damaged by bodily excretions, to lessen the friction of outerwear against the skin, to shape the body, and to provide concealment or support for parts of it. In cold weather, long underwear is sometimes worn to provide additional warmth. Special types of undergarments have religious significance. Some items of clothing are designed as undergarments, while others, such as T-shirts and certain types of shorts, are appropriate both as underwear and outerwear. If made of suitable material or textile, some underwear can serve as nightwear or swimwear, and some undergarments are intended for sexual attraction or visual appeal.
Undergarments are generally of two types, those that are worn to cover the torso and those that are worn to cover the waist and legs, although there are also underclothes which cover both. Different styles of underwear are generally worn by females and males. Undergarments commonly worn by females today include bras and panties (knickers in British English), while males often wear boxer briefs or boxer shorts. Items worn by both sexes include T-shirts, sleeveless shirts (also called singlets, tank tops, A-shirts, or vests), classic briefs, bikini briefs, thongs, G-strings and T-fronts.