A bikini is a two-piece swimsuit primarily worn by girls and women that features one piece on top that covers the breasts, and a second piece on the bottom: the front covering the pelvis but usually exposing the navel, and the back generally covering the intergluteal cleft and a little, some, or all of the buttocks. The size of the top and bottom can vary, from bikinis that offer full coverage of the breasts, pelvis, and buttocks, to more revealing designs with a thong or G-string bottom that covers only the mons pubis, but exposes the buttocks, and a top that covers only the areolae. Bikini bottoms covering about half the buttocks may be described as "Brazilian-cut".

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.