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 garments 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 undergarments and as outer clothing. If made of suitable material or textile, some undergarments can serve as nightwear or swimsuits, and some 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 garments which cover both. Different styles of undergarments are generally worn by females and males. Undergarments commonly worn by females today include bras and panties (known in the United Kingdom as knickers), while males often wear briefs, boxer briefs or boxer shorts. Items commonly worn by both sexes include T-shirts, sleeveless shirts (also called singlets or tank tops), bikini underwear, thongs, and G-strings.
Underwear is worn for a variety of reasons. They keep outer garments from being soiled by perspiration, urine, semen, menstrual blood and feces. Women's brassieres provide support for the breasts, and men's briefs serve the same function for the male genitalia. A corset may be worn as a foundation garment to alter a woman's body shape. For additional support and protection when playing sports, men often wear more tightly fitting underwear, including jockstraps and jockstraps with cup pocket and protective cup. Women may wear sports bras which provide greater support, thus increasing comfort and reducing the chance of damage to the ligaments of the chest during high-impact exercises such as jogging.
In cold climates, underwear may constitute an additional layer of clothing helping to keep the wearer warm. Underwear may also be used to preserve the wearer's modesty – for instance, some women wear camisoles and slips (petticoats) under clothes that are sheer. Conversely, some types of underwear can be worn for sexual titillation, such as edible underwear, crotchless panties and thongs.
Some items of clothing are designed exclusively as underwear, while others such as T-shirts and certain types of shorts are suitable both as underwear and as outer clothing. The suitability of underwear as outer clothing is, apart from the indoor or outdoor climate, largely dependent on societal norms, fashion and the requirements of the law. If made of suitable material, some underwear can serve as nightwear or swimsuit. <Video>