When you challenge someone, you invite them to compete or prove themselves. You might challenge your friend to a chess match, or challenge your sister to see who can solve a puzzle faster. A challenge is also the difficult task itself: climbing a mountain is a serious challenge, and so is learning long division or memorizing all fifty state capitals.

Challenges test what you can do. Some challenges are physical, like running a mile without stopping. Others are mental, like figuring out a ridiculously hard riddle. Challenges often push you just beyond what's comfortable, making you work and think harder than usual.

You can also challenge an idea or decision by questioning whether it's right. If a referee makes a bad call during a game, a coach might challenge the ruling. When scientists challenge old theories with new evidence, they're asking others to reconsider what everyone thought was true.

A challenge isn't the same as an impossible task. Good challenges are difficult but achievable if you put in real effort.