Vibration is a rapid back-and-forth movement that happens when something shakes or trembles. When you pluck a guitar string, it doesn't just move once: it moves back and forth hundreds of times per second, creating a blur of motion. That rapid movement is vibration.

Vibrations are everywhere around you. Your phone buzzes in your pocket because a tiny motor inside creates vibrations. When you speak, your vocal cords vibrate to produce sound. A washing machine vibrates during its spin cycle. An earthquake is a massive vibration of the Earth itself.

Different vibrations create different effects. Fast vibrations produce high-pitched sounds, while slow vibrations make low, rumbling sounds. Some vibrations you can see, like a plucked rubber band or a struck tuning fork. Others you can only feel, like the subtle vibration of a running car engine through the steering wheel.

Scientists measure vibrations in hertz, which counts how many times something vibrates per second. Understanding vibrations helps engineers design better buildings that can withstand earthquakes, helps musicians tune their instruments, and helps doctors use ultrasound machines to see inside the human body. Every sound you've ever heard began as a vibration traveling through the air to reach your ears.