To worry means to feel anxious or uneasy about something that might happen or go wrong. When you worry about an upcoming test, your mind keeps returning to thoughts like “What if I fail?” or “What if I forget everything I studied?” When a parent worries about a child who's late coming home, they imagine all the things that could have caused the delay.

Worry lives in your mind as persistent, uncomfortable thoughts about the future. It's different from fear, which responds to immediate danger. If a bear charges at you, that's fear. If you lie in bed thinking, “What if a bear comes to our campsite tonight?”, that's worry. Worry gnaws at you even when you're safe, making your stomach feel tight or keeping you awake at night.

Some worry is useful: it reminds you to study for tests or look both ways before crossing. But excessive worry can paralyze you, making it harder to think clearly or take action. When someone says “Don't worry about it,” they're telling you the problem either isn't serious or is beyond your control.

The word can also mean to bother or disturb something repeatedly, like when a dog worries a bone by chewing and shaking it. But the mental anxiety meaning is far more common.