A narrow opening or gap. The slot of a screwdriver is wide enough for the tip to pass through easily. To slot something into something else, as in He slotted the CD into the player.

A machine designed for gambling. A player inserts cash or, in “ticket-in, ticket-out” machines, a paper ticket with a barcode into a designated slot on the machine and then activates it by pushing a lever or button (physical or on a touchscreen). The reels spin and stop to rearrange the symbols; if the symbols match a winning combination on the paytable, the player earns credits according to the payout schedule. Most slots have a theme, and the symbols and bonus features align with that theme.

Casino officials say that slots now account for 85 percent of all profits in many jurisdictions, outpacing table games like blackjack and roulette. This is partly because players don’t have to wait around for a seat at a table and can play multiple machines at once.

The number of blank or paying symbol positions on a physical reel is limited by the circumference of the reel, so manufacturers used electronic circuits to create virtual reels that appear to the player as if they are real. These circuits weight particular symbols to cause them to appear more frequently than others, and to occupy a greater number of stops on the virtual reel than would be possible with a physical reel.

Some slot machines also have a variable house edge, which is the percentage of all money wagered that the machine returns to the player. The lower the house edge, the better the odds.