An hour is a unit of time equal to 60 minutes. It's one of the fundamental ways we measure and organize our days, which are divided into 24 hours.

Modern hours are exactly the same length whether it's day or night, but ancient hours actually changed with the seasons: a daylight hour in summer was longer than a daylight hour in winter.

We use hours to structure nearly everything: school might last six hours, you might have an hour of homework, or you might be allowed one hour of screen time. When someone says “I'll be there in an hour,” they mean about 60 minutes. If something takes “hours,” it means several of them, suggesting a long stretch of time.

You'll also hear hour used in special phrases. Your lunch hour might actually be only 30 minutes. Rush hour describes when traffic is heaviest, usually lasting longer than one hour. When something important happens, people call it someone's hour of need or their finest hour.

In conversation, people sometimes say “quarter of an hour” for 15 minutes or “half an hour” for 30 minutes. And when you're having fun, you might hear that “the hours flew by,” meaning time seemed to pass quickly.