In lotteries, numbers or symbols are drawn at random to select participants for prizes. The prize amount can be small or large. The odds of winning vary greatly, and the cost of a ticket may be high. In some cases, the prize money is paid out in installments or as a lump sum. Many lottery winners spend their winnings in ways that benefit society or improve their quality of life, but they also tend to save some of it.

The earliest known evidence of a lottery is a keno slip from the Chinese Han dynasty (205–187 BC), and it was used for financing public works projects. The modern lottery is a national or state-sponsored game, and it has become an important source of revenue for governments. Some people play a lottery every week, but others play less frequently. High school-educated, middle-aged men are the most frequent players of lotteries.

Several colonies used lotteries to finance private and public projects during the Revolutionary War, including roads, libraries, churches, schools, canals, bridges, and universities. Lotteries became more widespread in the United States after the Revolution, and the Continental Congress authorized state-sponsored lotteries.

Most state-sponsored lotteries are closed systems that allow only the sale of tickets to residents of the state or territory. Some lotteries are monopolies, and they exclude competing commercial lotteries and sell their profits to the government. The United States has forty lottery monopolies, and the total value of prizes awarded by these lotteries is $5.2 billion per year.