A slot is a narrow depression, notch, slit, or opening, especially one for receiving or admitting something, such as a coin in a machine. A slot may also refer to a position in a group, series, or schedule. For example, I have a meeting at 2 p.m., so I’m in the slot for that time.

In a slot machine, the player inserts cash or, in ticket-in, ticket-out machines, a paper ticket with a barcode, into a slot on the machine and activates it by pushing a lever or button (either physical or on a touchscreen). The reels spin and stop to rearrange symbols and award credits according to the paytable. Depending on the theme, a slot may feature classic icons such as fruit, bells, and stylized lucky sevens, or it can incorporate more elaborate video graphics and interactive features.

Modern slot machines use microprocessors that assign a different probability to each symbol on each reel. The result is that although a particular symbol might appear often on the visible reels, its odds of appearing on a payline are lower than for other symbols. Some manufacturers have experimented with increasing the house advantage by weighting particular symbols to make them appear less frequently on a reel, but this is not popular among casino operators who fear that players will quickly detect these price increases and leave their establishments. Consequently, the majority of slots continue to use visible reels.