Improper means not correct, not suitable, or not following accepted rules or standards. When something is improper, it's wrong for the situation or goes against what's expected.

In math, an improper fraction is one where the top number (numerator) is larger than the bottom number (denominator), like 7/4. It's called improper not because it's wrong, but because it doesn't follow the usual pattern where the top is smaller than the bottom.

In everyday life, improper behavior means acting in ways that break social rules or expectations. Shouting in a library would be improper because libraries require quiet. Wearing pajamas to a wedding would be improper because the situation calls for formal clothes. Using improper language might mean swearing or speaking rudely when politeness is expected.

The word can suggest that someone knows better but chooses to ignore the rules anyway. A properly installed bicycle helmet protects your head; an improperly installed one might slip off when you need it most. Improper use of tools can be dangerous. Improper planning can lead to problems later.

The opposite of improper is proper, which means correct, suitable, or following the right standards for the situation.