A slot is a narrow opening, especially one for receiving something, as a slit in a door or a hole in a wall. The word’s etymology is unclear; it may come from the Old English for groove or channel, or from the verb to slot, meaning to fit snugly. For example, a car seat belt slots easily into the buckle. A slot can also refer to a position in a sequence or series, as when someone says “I have a slot in the orchestra.”
In gambling, a slot is a reel that spins around and contains symbols that earn credits based on the paytable. A player inserts cash or, in “ticket-in, ticket-out” machines, a paper ticket with a barcode into the machine and activates it by pressing a lever or button (either physical or on a touchscreen). The reels then stop to reveal winning combinations of symbols and pay out according to the paytable. Symbols vary by machine, but classics include fruits, bells, and stylized lucky sevens. Many slots have themes, such as a specific locale or character, and bonus features align with the theme.
Air traffic slots are time periods during which an airline can operate at a congested airport, such as Heathrow. Airlines can compete to secure these slots, which are awarded by the slot coordinator at each airport. Since central flow management was implemented at many European airports, airlines have been able to avoid costly delays and save fuel by waiting for a slot rather than flying when it’s too full.