Unreasonable describes behavior, demands, or expectations that go far beyond what makes sense or what's fair to ask of someone. An unreasonable request is one that ignores reality or shows no consideration for others' limits.

If your teacher assigned 500 math problems for homework tonight, that would be unreasonable because it's impossible to finish in one evening. If your friend demanded you give them half your Halloween candy just for walking around the neighborhood with you, that would be unreasonable because they're asking for far more than they deserve. If someone refuses to accept clear evidence, like insisting the sun revolves around the Earth despite all scientific proof, they're being unreasonable.

The word often describes people who won't listen to logic or consider other viewpoints. An unreasonable person might throw a tantrum when they can't have everything exactly their way, or refuse to compromise even when their position makes no sense.

Notice that unreasonable is different from simply being wrong. You can make an honest mistake and still be reasonable. But when someone ignores facts, dismisses fairness, or makes impossible demands, they've crossed into unreasonable territory. The opposite is reasonable: sensible, fair, and willing to consider the actual circumstances.