An escalator is a moving staircase that carries people between different floors of a building. Stand on it, and it smoothly transports you up or down while you ride. Department stores, airports, and shopping malls use escalators to move large numbers of people efficiently between levels.

One of the first commercial escalators was shown at the Paris World's Fair in 1900, and it became an instant sensation. Before escalators, people had to climb regular stairs or wait for elevators. Escalators solved both problems: they move continuously, so there's no waiting, and you don't have to expend as much energy climbing.

Modern escalators can move thousands of people per hour. They're especially useful in subway stations, where crowds need to reach platforms quickly. Some escalators are incredibly long: the one in the Park Pobedy station in Moscow rises about 413 feet and takes about three minutes to ride.

The word has also become a verb. When something escalates, it intensifies or grows more serious, like an argument that escalates from a small disagreement into a major conflict. Just as an escalator carries you steadily upward, an escalating situation keeps moving toward something bigger.