To rework means to change or improve something by working on it again. When a teacher asks you to rework a paragraph in your essay, she wants you to revise it, making it clearer or stronger than your first attempt. When an engineer reworks a design, he adjusts the plans to fix problems or make the product work better.

The word suggests substantial changes that require real effort. If you rework something, you're putting effort into reshaping it, making significant improvements rather than just correcting small errors. A composer might rework a melody, changing the notes and rhythm to create a better effect. A chef might rework a recipe, adjusting ingredients and cooking times until the dish tastes just right.

Sometimes rework happens because the first version had flaws. Other times you rework something good to make it even better. Either way, reworking takes patience and skill. You have to look carefully at what you've already done, figure out what needs changing, and then do the hard work of making those changes.