Length is how long something is from one end to the other. When you measure the length of your bedroom, you're finding the distance from one wall to the opposite wall. A swimming pool's length might be 25 meters, while a pencil's length might be just 7 inches.

Length is one of the fundamental measurements we use to describe the physical world, along with width and height. Carpenters measure the length of boards before cutting them. Track runners compete in races of different lengths: 100 meters, 400 meters, or longer. When you hear that a movie is “feature length,” it means it's long enough to be a full movie, usually over 90 minutes.

The word also describes duration, particularly for movies, books, or speeches. A lengthy explanation goes on for a while, maybe longer than necessary. If your teacher says “let's discuss this at length,” she means you'll talk about it thoroughly and in detail, taking whatever time is needed.

People also use length figuratively. Going to great lengths means making extraordinary efforts to achieve something. If someone goes to great lengths to help a friend, they're doing everything possible, even if it's difficult or inconvenient.