Gambling is the act of betting or staking something of value on the outcome of a game, a contest, or an uncertain event whose outcome may be determined by chance or accident, or may have an unexpected outcome due to the bettor’s miscalculation.

Gambling game outcomes can be determined solely by chance, such as the purely random activity of a tossed pair of dice or the ball on a roulette wheel, or by physical skill, training, or prowess in athletic competitions, or by a combination of strategy and chance. The rules that govern gambling games can sometimes obscure the relationship between the game’s components, which are based on skill and chance, allowing some players to manipulate the game to their advantage. Thus, understanding the game is beneficial when playing poker or betting on horse races, but it is useless when buying lottery tickets or playing slot machines.

A gambler can either play the game while betting on the outcome (card games, craps), or he can be barred from participating in any way in an event in which he has a stake (professional athletics, lotteries). Without the accompanying betting activity, some games are dull or nearly meaningless, and they are rarely played unless wagering is involved (coin tossing, poker, dice games, lotteries). In other games, betting is not an integral part of the game, and the association is purely coincidental and not required for the game’s success (horse racing, football pools). Commercial establishments such as casinos and racetracks may organise gambling if a portion of the money wagered by patrons can be easily obtained by participating in the game as a preferred party, renting space, or withdrawing a portion of the betting pool. Some large-scale activities (horse racing, lotteries) necessitate the use of commercial and professional organisations to effectively present and maintain them.

Prevalence of major types

The amount of money legally wagered annually in the world is estimated to be around $10 trillion (illegal gambling may exceed even this figure). Lotteries are the most popular kind of gambling in the world in terms of overall revenue. During the late twentieth century, state-licensed or state-operated lotteries grew rapidly in Europe and the United States, and are now found all over the world. Nearly every European country, several South American countries, Australia, and a few African and Asian countries have organised football (soccer) pools. In most of these countries, state-organized or state-licensed wagering on other sporting events is also available.

Horse racing betting is a popular type of gambling in English-speaking countries, as well as in France. It is also found in a number of other nations. Horse racing has usually become a major business wherever it is popular, with its own newspapers and other periodicals, extensive statistical services, self-styled experts who sell betting advice, and sophisticated communication networks that provide information to betting centres, bookmakers and their employees, and workers involved in horse care and breeding. Dog racing is similar, albeit to a lesser extent. With the advent of satellite broadcasting technology, so-called off-track betting facilities have sprung up, where bettors can view live telecasts from sites other than the racetrack.

Chances, probabilities, and odds are all terms used to describe how likely something is.

Equally probable events or outcomes have an equal possibility of occurring in each case. In pure chance games, each instance is totally independent; that is, each play has the same chance of achieving a given outcome as the others. In actuality, probability statements apply to a long series of events but not to single events. The law of big numbers refers to the notion that whereas probability statements predict ratios with increasing accuracy as the number of events grows, the absolute number of outcomes of a given kind deviates from expectation with increasing frequency as the number of repeats grows. Individual events and specific totals are not accurately predictable, but ratios are.