A narrow notch, groove, or opening, as in a keyway in machinery or a slit for a coin in a vending machine. Also: (informal) a position, time, or opportunity for doing something: I had to wait in line for a long time to get my slot at the movies.

In the old days, slots were all-or-nothing affairs: You yanked a lever and either all the cherries or lucky sevens lined up to pay you money or they didn’t. But by the 2000s, better computer technology allowed casinos to offer games with higher jackpots while still having precise control over odds and percentage payback.

A slot is also the term used for the specific authorization that an airport or air-traffic controller grants a plane to take off or land during a certain time period. This is an important tool to help manage traffic at busy airports, as it reduces repeated delays that occur when too many flights try to operate at the same time.