A slot is a narrow aperture or groove, such as a keyway in a machine, a slit in a door, or a compartment for coin in a vending machine. A slot can also refer to a position in a sequence, series, or set of activities. In computer hardware, a slot is an area of a motherboard with close-spaced holes for connection pins that can be used to attach an expansion card containing circuitry that adds a specialized capability, such as video acceleration or disk drive control. Almost all desktop computers come with several expansion slots.

A slot can also refer to a specific time of day, particularly on a weekend. Having a planned weekend activity can help you avoid procrastination and get the tasks on your to-do list finished. The best way to do this is to decide during the week exactly what you are going to achieve, and then plan how to fit it all in.

In aviation, a slot is a reservation of air traffic capacity that allows airlines to fly through congested areas without having to wait on the ground or burn excess fuel. This system of flow management has led to significant savings for airlines and has also improved environmental efficiency. Airport slots are often highly coveted and can be traded. In Europe, the slots are administered by EUROCONTROL as part of its Air Traffic Management role. In other countries, they may be assigned by national authorities.