A slot is a specific time or place for an aircraft to take off or land, allocated by an air-traffic control authority. It is also a position or job: He was offered the slot as chief copy editor at the Gazette.
A mechanical slot machine accepts cash or, in “ticket-in, ticket-out” machines, a paper ticket with a barcode that is swiped or otherwise read to activate the reels and pay out credits according to the machine’s paytable. Modern slot machines use random number generators to determine which symbols appear on each reel.
Each possible combination is assigned a different probability, and the random-number generator sets those probabilities when it receives a signal, which can be anything from a button being pushed to the handle being pulled. This explains why you might feel the winning symbol was “so close” or that a certain machine is always hot, even though each spin has exactly the same probability of hitting any given symbol.
Many people believe that a slot machine that has gone long without paying off is due to hit, and this belief accounts for why slots are often placed at the end of casino aisles or in front of high-traffic areas. But a machine that has gone long without paying doesn’t necessarily mean it’s “due” to win — it might just be unlucky. A better indicator of whether a machine is loose or not is to test the payout percentage by placing a bet and then seeing how much it pays back.