When you think of slot, you might imagine an old-fashioned mechanical machine with metal coin trays and clangs and clatter of tokens or coins. These machines are now the dominant force in the gambling industry, accounting for 85 percent of profits. And though they have a bad reputation for being addictive, psychologists believe that they can be just as damaging to gamblers as blackjack or roulette.

Generally, when a player inserts cash or, in ticket-in, ticket-out machines, a paper ticket with a barcode, the machine activates a series of reels that display symbols. When the machine stops, it awards credits based on a pay table, which lists the payouts for various combinations of symbols. Each symbol has a specific weighting, which determines how often it appears on a given physical reel. Some modern machines use computer programs to adjust the odds and weightings automatically.

A slot is a narrow opening, slit, or groove. It can also refer to a position, assignment, or location. For example, a player may be assigned a particular time slot to work on a project or task. She slotted the new filter into the machine. A slot can also refer to an area on a page or in a document, such as the space in which to write. The term is also used in sports to describe the unmarked area of ice hockey rink between the face-off circles. (From The American Heritage® Dictionary of the English Language, Fifth Edition.)