The ball eventually loses momentum, passes through an area of deflectors, and falls onto the wheel and into one of thirty-seven (single-zero, French or European style roulette) or thirty-eight (double-zero, American style roulette) or thirty-nine (triple-zero, 'Sands Roulette') colored and numbered pockets on the wheel. To determine the winning number, a croupier spins a wheel in one direction, then spins a ball in the opposite direction around a tilted circular track running around the outer edge of the wheel. In the game, a player may choose to place a bet on a single number, various groupings of numbers, the color red or black, whether the number is odd or even, or if the numbers are high (19–36) or low (1–18). Roulette (named after the French word meaning 'little wheel') is a casino game which was likely developed from the Italian game Biribi.

Roulette ball 'Gwendolen at the roulette table' – 1910 illustration to George Eliot's ' Daniel Deronda'.

For other uses, see Roulette (disambiguation).

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