A lottery is a gambling game in which a person buys a ticket for a chance to win a prize. Prizes are generally cash, but other prizes may include goods, services, or land. Some states prohibit lotteries, while others endorse them and regulate them. Most state lotteries are operated by a government agency or public corporation (as opposed to private firms that receive a percentage of profits from the sale of tickets). Since 1964, when New Hampshire introduced a lottery, nearly every state has followed suit and today 38 states and the District of Columbia operate lotteries. Despite their enormous popularity, lotteries are subject to persistent criticism centered on issues such as compulsive gambling and the alleged regressive effect on lower-income groups.

The most basic elements of a lottery are:

A mechanism for collecting and pooling money placed as stakes; a set of rules determining the frequency and size of prize winnings; and a procedure for allocating those prizes. In some lotteries, bettor names and the amount staked are written on tickets; in others, the bettor simply writes a number or symbol on a slip of paper that is deposited with the lottery organization for subsequent shuffling and selection in a drawing.

Most people consider buying a lottery ticket a reasonable risk-to-reward investment, even though the odds of winning are incredibly slight. Purchasing a lottery ticket does not cost much in monetary terms, but for many players it is an investment of time and energy—and often thousands of dollars that they would otherwise spend on retirement or college tuition savings. In such cases, the entertainment value or other non-monetary benefits that are obtained are sufficiently high to outweigh the disutility of a monetary loss.