Negligent means failing to take proper care or attention when you're supposed to be responsible for something. When someone is negligent, they're not being careful enough, and their carelessness can cause problems or even harm.

A lifeguard who spends the whole day texting instead of watching swimmers is being negligent because they're ignoring their duty to keep people safe. A pet owner who doesn't feed their dog for days is being negligent because they're failing in their responsibility to care for an animal that depends on them.

The word carries more weight than simply “careless.” Negligent suggests that someone had a real responsibility and failed to meet it. If you accidentally bump into someone in a crowded hallway, that's an accident. But if a construction company skips important safety checks and someone gets hurt, that's negligence.

Parents, doctors, teachers, and many other people can be held responsible for negligence if they fail to do what they're supposed to do to keep others safe. The related noun negligence describes this kind of careless behavior. Courts sometimes have to decide whether someone's negligence caused an accident or injury, which is why the concept matters in law as well as everyday life.