To be cautious means to be careful and thoughtful about possible dangers or problems before acting. A cautious person doesn't rush into situations without thinking them through first.

When you're cautious crossing a busy street, you look both ways twice and wait for a safe gap in traffic. When scientists test a new medicine, they're cautious by running many experiments before giving it to patients. A cautious chess player thinks several moves ahead, considering what could go wrong with each strategy.

Being cautious doesn't mean being scared or timid. It means using your brain to avoid unnecessary risks. A rock climber can be both brave and cautious by checking their equipment carefully before climbing. A cautious student might read test instructions twice to make sure they understand what's being asked.

The opposite of cautious is reckless or careless. Someone who runs down stairs without looking, or who agrees to something without asking questions first, isn't being cautious. The word caution (the noun form) means the quality of being careful, and it can also mean a warning, like when someone says “use caution when handling scissors.”

People might tell you to “proceed with caution” when entering unfamiliar territory, or to “err on the side of caution,” meaning it's better to be a little too careful than not careful enough.