A slot (pronounced slit) is a narrow notched or grooved opening, as in a keyway in a piece of machinery or a slit for a coin in a vending machine. It may also refer to a position or time in a sequence or schedule: I can slot you in at 2 p.m.

In computer hardware, a slot is an empty area in a motherboard that supports expansion cards. The slots are typically arranged in rows on the board with each row holding a specific type of card. The slots can be filled with ISA, PCI, or AGP expansion cards. A slot is sometimes referred to as a “lane” or an “slot width”.

The first slot machines used mechanical reels to display and determine results. They were a huge success, but had many problems. For example, electromechanical machines had “tilt switches”, which would make or break a circuit when the machine was tilted, and this often caused the machine to pay out even if it was not a winning combination. In addition, there was only a cubic number of possible combinations for a machine with three physical reels; this limited jackpot sizes.

In the late 19th century, a San Francisco mechanic named Charles Augustus Fey created a simpler and more reliable machine, the Liberty Bell. The machine was a huge success, and it led to the development of modern slot machines, which use electrically controlled reels to display and determine winning combinations.