A narrow notch, groove, or opening, as a keyway in machinery or a slit for a coin in a vending machine. Also: A position in a group, series, or sequence, such as the one occupied by the chief copy editor.
A machine that pays out a prize when a particular combination of symbols appears on the reels, such as a cherry, bell, or lucky seven. Invented by Charles Fey, a mechanic in San Francisco, the first slot machines had three spinning reels emblazoned with symbols like diamonds, spades, hearts, and horseshoes that lined up to make poker hands when spun. The earliest ones were operated by pulling a lever; later, they were controlled by computer chips.
In modern slot machines, the number of possible symbols on each reel increased to 22, but microprocessors made it easy for manufacturers to weight the probability that a particular symbol would appear on a given reel. This can give the impression that a certain symbol is “so close” to winning, even though the odds of it appearing are actually much lower.
Skilled players can exploit this phenomenon by looking for patterns in the appearance of specific symbols. They can then try to predict when a particular symbol is likely to show up, and thus maximize their chances of winning. This article covers normal slots; a separate page discusses new skill-based slot games that combine elements of video games with traditional gambling.