A slot is an opening, position or vacancy in a group, series or sequence. The word is also used in aviation to describe a time period when an aircraft can take off or land at an airport. For example, an airline might be given a flight slot based on the number of people that need to get to their destination at that hour. Airlines may also be given slots for specific flights where the traffic flow is constrained and it is not possible to schedule all the departures and arrivals at the same time.

On a computer, a slot is the area of memory (and sometimes the data path machinery) that shares the operations with the rest of the machine. This is different from a register, which shares its memory with all other registers. The slot concept is important in very long instruction word (VLIW) computers.

A player inserts cash or, in ticket-in, ticket-out machines, a paper ticket with a barcode into a designated slot on the machine to activate it. The reels then spin and stop to rearrange the symbols in order to form a winning combination of paylines. When a combination is completed, the player earns credits according to the paytable. Some slot machines allow players to choose the number of paylines they want to run during a game, while others have a fixed number that cannot be changed. Free slots have a higher return-to-player percentage (RTP) than fixed slot machines.