A narrow notch or groove, as in a keyway or slit for a coin on a machine. Also: a position or assignment, as in a series, sequence, or game.

In casinos, slot is a type of gambling machine that accepts paper tickets or electronic cards with barcodes to track player activity and reward loyalty points. Modern slot machines feature video screens instead of mechanical reels and use microprocessors to assign a probability to each stop on the multiple-reel display. This allows them to appear to have a high hit frequency, but the actual odds of getting a particular symbol on a payline are lower than the overall probability of winning a jackpot. This can lead to false perceptions about the probability of hitting a specific symbol, and can cause people to gamble longer than they would if they knew their chances of winning were low.

The term “slot” has also been applied to games of chance where a large prize (such as a car) is offered to the winner of a single hand of poker or a lottery draw, and to situations in which winnings are accrued over a period before payment is made, such as in casino or lottery games. The term may also refer to the smallest unit of gambling activity, such as a spin or a chip in a poker game.

A “slot” in the context of air traffic management is a time or duration assigned to an airline for use of a runway or other airport facility, typically when such capacity is constrained (as at many European airports). Air traffic control slots are used by EUROCONTROL as part of its Network Manager role.