A slot is a gap in a schedule or sequence. The term also refers to a position, or the part of one’s body that occupies this position, or to a vacancy for a particular activity. A slot is an opening or channel, usually narrow, through which something may be inserted. One may “slot” a coin into a slot machine or slide a card into a slot in a lock.
In a slot machine, a player inserts cash or, in “ticket-in, ticket-out” machines, a paper ticket with a barcode into a designated slot, which activates reels that spin and stop to rearrange symbols and award credits based on the paytable. The number of possible combinations of symbols is limited, but the payouts can be substantial. Modern slot games typically have a theme, such as a specific style, location, or character, and the symbols are aligned with that theme.
As microprocessors became ubiquitous, manufacturers of slot machines programmed them to assign a different probability to each symbol on each reel. This meant that a given symbol would appear only once on the reel displayed to the player, even though it might actually be present on multiple stops on the physical reel. Hence, it could look to players like a winning symbol was so close, when in fact the odds were much lower. This is the “near-miss” effect.