A slot is a narrow opening, especially one in a machine or container, into which something can be inserted. It can also refer to a position within a sequence or series, or an assignment or job opportunity. The word is derived from Middle Low German slot, from slit and Old English slott. The sense “narrow opening into which something can be fitted” is attested from 1520s; that of “position in a sequence or series” is from 1888 (slot machine).

On a slot machine, a player inserts cash or, in ticket-in, ticket-out machines, a paper ticket with a barcode, then activates the reels by pressing a lever or button (physical or virtual), which spin and stop to arrange symbols. When a winning combination appears, the player receives credits based on the pay table. Symbols vary from machine to machine, but classic symbols include fruits, bells, and stylized lucky sevens.

A quarter slot is the best type of slot for people on a budget, as it yields higher value than nickel and penny slots but is not too expensive or risky. Many slots allow players to choose the number of paylines they want to run during a game; this is considered a ‘free slot’, while those that require the player to wager on all available paylines are known as ‘fixed slots’.