Zero
The single green pocket that no even-money, dozen or column bet covers; the source of the house edge. Also: single zero, 0.
In context
Zero wins for inside betsbetInside betAny bet placed on or between the numbers of the grid: straight up, split, street, corner, six line.Read full → that include it and loses for every outside betbetOutside betA bet on the boxes surrounding the grid: dozens, columns and even-money bets.Read full →, unless la partageruleLa partageFrench rule: when zero hits, half of an even-money stake is returned. Halves the house edge on those bets to 1.35%.Read full → or en prisonruleEn prisonFrench rule: when zero hits, an even-money bet is held for the next spin instead of lost. Halves the house edge on those bets.Read full → applies.
Green was chosen so that zero would be neither redbetRedEven-money bet on the 18 red numbers. French: rouge.Read full → nor blackbetBlackEven-money bet on the 18 black numbers. French: noir.Read full → and no color bet could claim it. Early wheels used other colors, and at least one 18th-century layoutequipmentLayoutThe printed betting grid on the table. Also: table, felt, cloth.Read full → had the zeros in red and black, which caused exactly the arguments you would expect.