A place for a printed circuit board (PCB) in a computer. Also referred to as an expansion slot, an ISA slot, a PCI slot, and an AGP slot. It may be a metal box with holes, or a plastic socket in which a printed circuit board is placed.

A slot is a small opening in the side of a computer tower that accommodates expansion boards, which add to its functionality. Depending on the model of a computer, the slots can be used to hold expansion cards, hard disk drives, optical disc drives, and memory. They can also be used to connect peripheral devices, such as printers and scanners. A slot is not to be confused with bays, which are sites in the front of a computer for installing disk drives.