Sane means having a healthy, rational mind that works the way it should. A sane person can think clearly, understand reality accurately, and make reasonable decisions. When someone acts in a sane way, they're behaving sensibly and logically given the situation they're in.

The opposite is insane, which describes someone whose mind isn't functioning properly, leading them to believe things that aren't true or act in ways that don't make sense. In legal contexts, courts sometimes must determine if someone was sane enough to understand right from wrong when they committed a crime.

People also use sane more casually to mean sensible or reasonable. You might say “No sane person would try to ride their bike through a thunderstorm” or describe a friend's careful planning as “the only sane approach.” In these cases, you're not making a medical judgment about anyone's mental health, just pointing out that something would be foolish or irrational.

The word sanity means the state of being sane. After a chaotic day of noise and confusion, you might joke about needing peace and quiet to protect your sanity. People sometimes talk about staying sane during difficult times by taking care of themselves, like getting enough sleep, talking to people they trust, and taking breaks when they need them.