A lottery is an arrangement in which one or more prizes are allocated by chance, and for which some sort of consideration (often money) is paid by the participants. The term is also applied to any game or process in which a drawing is held for a prize. Lottery laws generally prohibit the mailing or transportation in interstate or foreign commerce of promotions for lotteries and the transmission of lottery tickets themselves.

In general, state governments adopt lotteries to raise funds for public purposes. These proceeds are supposed to supplement regular tax revenues. The prevailing argument is that people buy tickets with the understanding that they will benefit some specific public good, such as education. But research suggests that this message has little bearing on the overall popularity of the lottery and that the objective fiscal circumstances of states do not play a major role in determining whether or when they adopt one.

Many people see a lottery ticket as a risk-free investment: For just a few dollars, they can dream about winning a fortune. For some, however, the gamble is not so benign. Numerous studies show that lottery players disproportionately come from the poorest households, and critics complain that this is a hidden tax on those least able to afford it. Still, most people buy tickets and many consider their participation a form of civic duty. And the fact remains that, in spite of their long odds, someone has to win.