A roof is the top covering of a building that protects everything inside from rain, snow, sun, and wind. Every house, school, and store has a roof, though they come in different shapes: some are flat, some slope gently, and others are steeply pitched to shed snow or rain quickly.

The phrase “a roof over your head” means having shelter and a place to live. When people say someone “raised the roof,” they mean the celebration or noise was so loud and energetic it seemed like it might lift the building's top right off. If you “hit the roof,” you're suddenly very angry, like your temper shot straight up.

Roofs need to be strong and carefully built. Throughout history, people have made roofs from whatever materials they had: grass and mud, wooden shingles, clay tiles, slate, or modern asphalt. A roofer is someone whose job involves building and repairing roofs, often working high above the ground where one wrong step could lead to a dangerous fall.

In math and everyday conversation, roof can refer to the highest point or maximum limit of something, like when someone says prices are “going through the roof.”