A narrow notch, groove, or opening, as in a keyway in machinery or a slit for a coin in a slot machine. Also, (in computing) a space on a computer motherboard in which a plug-in card may be inserted to add functionality. See also expansion slot.

In a slot game, players insert cash or, in “ticket-in, ticket-out” machines, paper tickets with barcodes into a designated slot, which activates reels that spin and stop to display symbols. When the symbols line up in a winning sequence, the player receives credits based on the paytable. Each slot typically has one or more pay lines, which can run horizontally, vertically, diagonally, or in a zigzag pattern.

If the player wins, the credits are added to their balance. If they lose, their balance is reduced by the amount wagered. If the player has enough balance, they can try again. However, the odds of winning are still against them, because the random-number generator has dozens of possible combinations running at once. Each time the machine is activated, it sets a different combination of numbers and starts spinning. To hit the same combination as someone else requires almost perfect split-second timing.

Some critics of slot machines have argued that increased hold is decreasing the average length of slot sessions. Others have countered that, given the fixed cost of operating a machine, increases in hold can only decrease average time spent on the machine. These example sentences are automatically selected and may contain sensitive content.