A seatbelt is a safety strap in a car, airplane, or other vehicle that holds you securely in your seat during sudden stops, turns, or crashes. When you buckle your seatbelt, you pull the fabric strap across your lap and chest and click it into a metal buckle until you hear a snap.

Seatbelts work by spreading the force of a sudden stop across the strongest parts of your body: your hips and chest. Without a seatbelt, if a car stopped suddenly, your body would keep moving forward at whatever speed the car had been traveling. You could slam into the dashboard, windshield, or front seat with tremendous force. The seatbelt catches you and slows you down along with the car.

Modern cars include seatbelts because they save thousands of lives every year. In fact, wearing a seatbelt reduces your risk of serious injury in a crash by about half. Many places have laws requiring everyone in a vehicle to buckle up.

The term can also be used as a verb: you might tell your little brother to seatbelt himself before the car starts moving. Some people call seatbelts safety belts or use the British term seat belt (two words), but they all mean the same thing.