Unsure means not confident or certain about something. When you're unsure whether you locked your bike, you can't quite remember if you did it or not. When a student is unsure of an answer on a test, they're not confident they've got it right.

Being unsure is different from being completely clueless. If someone asks you a question in a language you don't speak, you're not unsure, you simply don't know. But if your teacher asks whether the American Revolution started in 1775 or 1776, and you think it might be 1775 but you're not totally confident, that's being unsure. There's a nagging doubt in your mind.

People show they're unsure in different ways. Someone might say “I think so” with a questioning tone, or “maybe” or “I'm not really sure.” They might hesitate before answering or furrow their brow while thinking.

Recognizing when you're unsure rather than pretending to be certain can be helpful. A scientist who's unsure about their results might run more experiments. A person who's unsure about directions might check a map rather than guessing and getting lost.