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".

A swimsuit is an item of clothing designed to be worn by people engaging in a water-based activity or water sports, such as swimming, diving and surfing, or sun-orientated activities, such as sun bathing. Different types may be worn by men, women, and children. A swimsuit can be described by various names, some of which are used only in particular locations or for particular types of suit, including swimwear, bathing suit, bathing attire, swimming costume, bathing costume, swimming suit, swimmers, swimming togs, bathers, cossie, or swimming trunks, besides others.