A lottery is a system of public gambling in which prizes are allocated by a process that relies on chance. It typically involves the use of a pool or collection of tickets or their counterfoils, from which winning numbers or symbols are selected in a drawing. Often, the tickets or counterfoils are thoroughly mixed by mechanical means such as shaking or tossing. More recently, computers have been used to randomly mix and select the winners.

Lotteries have been widely used throughout history to fund a variety of purposes. They were especially popular in colonial-era America, where they raised funds to pave streets, erect wharves, and build churches. Benjamin Franklin even sponsored a lottery to raise money for cannons to defend Philadelphia against the British during the American Revolution, but his efforts were unsuccessful.

Many people try to increase their odds of winning the lottery by purchasing all the possible combinations of numbers. While this may not work with the large lotteries like Mega Millions or Powerball, it can be effective for smaller state-level lotteries. In fact, Romanian-born mathematician Stefan Mandel once managed to win 14 times in a row with a system that involved getting 2,500 investors to buy all the combinations of numbers.

Almost 186,000 retailers sell state-run lottery tickets in the United States. These include convenience stores, drugstores, grocery stores, gas stations, service stations, restaurants and bars, and some nonprofit organizations (such as fraternal organizations and churches). In addition to lottery ticket vendors, some state governments offer lottery games online.