To deplete means to use up or reduce the supply of something, often to the point where there's very little or nothing left. When a video game character's health bar depletes during a battle, it drops lower and lower until they might have almost no health remaining. When you deplete the battery on your tablet by playing games all afternoon, you drain its power until it needs recharging.

The word often describes resources that run low through use. A water bottle gets depleted as you drink from it during a long hike. A town's emergency supplies might become depleted after a severe storm. Scientists worry about depleting natural resources like fossil fuels or clean water if we use them faster than Earth can replace them.

When something is depleted, it feels empty or exhausted. You might feel depleted after a hard day of physical activity, meaning your energy is used up. A depleted bank account has very little money left in it. The key idea is that something once full or abundant has been drawn down through use, leaving less than before.

Notice that deplete is stronger than just “use” because it emphasizes using so much that you're running dangerously low. You use a pencil, but you deplete your entire supply of pencils when you've gone through them all and need to buy more.