A bikini is a two-piece swimsuit for women.
The top part is shaped like a bra and the bottom part is a pair of briefs, which may resemble hotpants, a tanga or a thong. The term bikini bottom or bikini briefs is sometimes used for very tight brief shorts.
In most contexts, the bikini represents the minimum garments that women can wear in public in Western cultures and still be considered "decent", and it often has sexual associations. So "bikini contests" can be somewhat revealing displays of female beauty which do not violate public nudity laws or cross over into explicitly erotic entertainment, etc.
A suspender thong has been described as a one-piece bikini or a sling bikini.
One of the earliest representations of bikini-like garments is found in 3rd-century mosaics in the Roman villa of Casale near Piazza Armerina, Sicily, where women are shown exercising and athletically competing (but not swimming) in red strapless bikinis. In modern times, bikini-like garments existed in the early 20th century, but as part of elaborate show-girl performing costumes (not swimwear), and were not worn by ordinary respectable women.
The bikini was introduced as swimwear in 1946, with the name taken from the Pacific atoll site of a recent atomic bomb test, since the bikini was supposed to have the same explosive effect on a male viewer. It did not fully catch on until the beginning of the 1960s. The first syllable of the word "bikini" was later interpreted (etymologically incorrectly) as the prefix bi-, meaning "two", to form the punning word monokini, used to mean a swimsuit consisting only of the bikini bottom (leaving the breasts uncovered).
In the 1970s, the adjustable "string bikini" was introduced, starting a long-term trend towards ever-skimpier varieties of bikini (especially in Brazil).