A pedometer is a small device that counts your steps as you walk or run. The name comes from the Latin word pedis, meaning foot, and meter, meaning measure: it's literally a foot-measurer.

Most pedometers clip onto your belt or fit in your pocket, using a tiny sensor that detects the up-and-down motion of walking. Every time you take a step, the device registers it and adds one to its count. Some pedometers just count steps, while fancier ones estimate how far you've walked and how many calories you've burned based on your stride length.

Modern smartphones have built-in pedometers through apps that track your daily movement. Many people use pedometers to set fitness goals, like trying to walk 10,000 steps a day. Teachers sometimes use them in PE class to help students understand how much they move during different activities.

Today's electronic pedometers are far more accurate than early mechanical versions, but the basic idea remains the same: keeping track of how much you move throughout your day.