To improve means to make something better than it was before. When you practice piano every day, your playing improves: you make fewer mistakes, your fingers move more smoothly, and the music sounds more beautiful. When a writer improves her essay, she might strengthen weak sentences, add clearer examples, or fix confusing parts.

Improvement happens through effort and attention. A basketball player improves his free throw by analyzing what goes wrong and adjusting his technique. A student improves her grades by studying more effectively, asking questions when confused, and learning from mistakes. Scientists improve their experiments by testing different approaches and carefully observing what works.

The word suggests progress and growth rather than perfection. You might improve a recipe by adding more spices, or improve your treehouse by building a better ladder. Sometimes improvement takes time: learning to swim well means improving gradually through practice, not becoming perfect overnight.

Notice that improve focuses on the action of making things better, while improvement (the noun) refers to the better state itself or the process of getting there. When your teacher says your handwriting shows improvement, she means it's gotten noticeably better than before.