A narrow depression, groove, notch, or slit, especially one for receiving or admitting something, as a keyway in machinery or a slit for a coin in a vending machine. Also: a slot on a program, timetable, or broadcasting schedule; a position having a particular grammatical function within a construction: Compare filler (def 1).

In electromechanical slot machines, the number of stops on each reel was limited to about 22 allowing only about 10 648 combinations, so that winning and losing symbols had approximately equal chances of appearing on a payline. But manufacturers soon incorporated microprocessors into their machines, and could program each symbol to have a different probability of being picked on the payline compared with other symbols on that reel. This gave the appearance that a specific symbol was much more likely to appear than it really was.

Nowadays, slots have many extra features that increase their appeal to casino players. These include free spins – an extra spin of the reels awarded without paying anything – and multipliers, such as 2X or 3X symbols that multiply your winnings. There are also progressive multipliers where the amount you win is increased with each subsequent spin.

Another trend in slots is the addition of story elements, such as characters and setting. These add to the enjoyment of playing a game and can even trigger bonus mini-games. These are called i-Slot games and help to keep younger generations of casino gamers engaged in the gambling experience.