A lottery is a form of gambling which involves the drawing of lots for a prize. Some governments outlaw it, while others endorse it to the extent of organizing a national lottery. It is common to find some degree of regulation of lottery by governments.

At the beginning of the 20th century, most forms of gambling, including lotteries and sweepstakes, were illegal in many countries, including the U.S.A. and most of Europe. This remained so until after World War II. In the 1960s casinos and lotteries began to appear throughout the world as a means to raise revenue in addition to taxes.

Lotteries come in many formats. The prize can be a fixed amount of cash or goods. In this format there is risk to the organizer if insufficient tickets are sold. More commonly the prize fund will be a fixed percentage of the receipts. A popular form of this is the "50-50" draw where the organizers promise that the prize will be 50% of the revenue. Many recent lotteries allow purchasers to select the numbers on the lottery ticket resulting in the possibility of multiple winners.

The purchase of lottery tickets by large numbers of people is arguably economically irrational. However, in addition to the chance of winning, the ticket may enable some purchasers to experience a thrill and to indulge in a fantasy of becoming wealthy. If the entertainment value (or other non-monetary value) obtained by playing is high enough for a given individual, then the purchase of a lottery ticket could actually represent a gain in overall utility. In such a case, the monetary loss would be outweighed by the non-monetary gain, thus making the purchase a rational decision for that individual.

Early history

The first recorded signs of a lottery are Keno slips from the Chinese Han Dynasty between 205 and 187 B.C. These lotteries are believed to have helped to finance major government projects like the Great Wall of China. From the Chinese "The Book of Songs" (second millennium B.C.) comes a reference to a game of chance as "the drawing of wood", which in context appears to describe the drawing of lots. From the Celtic era, the Cornish words "teulet pren" translates into "to throw wood" and means "to draw lots". The Iliad of Homer refers to lots being placed into Agamemnon's helmet to determine who would fight Hector.

The first known European lotteries were held during the Roman Empire, mainly as an amusement at dinner parties. Each guest would receive a ticket, and prizes would often consist of fancy items such as dinnerware. Every ticket holder would be assured of winning something. This type of lottery, however, was no more than the distribution of gifts by wealthy noblemen during the Saturnalian revelries. The earliest records of a lottery offering tickets for sale is the lottery organized by Roman Emperor Augustus Caesar. The funds were for repairs in the City of Rome, and the winners were given prizes in the form of articles of unequal value.