A contusion is the medical term for a bruise. When you bump your shin on a table leg or fall on the playground and hit your arm, broken blood vessels under your skin leak blood into the surrounding tissue, creating that familiar purple or blue mark. That's a contusion.

Doctors and nurses use this word instead of “bruise” when they're being precise about injuries. If you've ever heard someone say they have a “bone contusion,” they mean a deep bruise on the bone itself, which hurts more and takes longer to heal than an ordinary bruise on the skin.

The color changes you see as a bruise heals (purple to green to yellow) happen because your body is breaking down and reabsorbing the leaked blood. Most contusions are minor and heal on their own within a week or two. Serious contusions, though, especially to the head, need medical attention because they might indicate a more significant injury underneath.

While “bruise” works perfectly fine in everyday conversation, knowing the medical term helps you understand what doctors mean when they examine an injury. Whether you call it a contusion or a bruise, it's your body's visible reminder to be more careful around that coffee table.