Swelling is when part of your body puffs up and becomes larger than normal, usually because of injury, infection, or irritation. When you twist your ankle playing soccer, it might swell up like a small balloon as fluid rushes to the injured area. A bee sting causes swelling around the spot where you got stung. Your gums might swell if you have a tooth infection.

Swelling happens because your body is trying to protect and heal itself. Extra blood and fluid flow to the damaged spot, bringing white blood cells to fight infection and repair tissue. That's why a swollen area often feels warm and looks puffy. While swelling can be uncomfortable, it's usually a sign your body's defense system is working.

The word also means growing or increasing, like swelling with pride when you accomplish something difficult, or the swelling sound of an orchestra getting louder during a dramatic moment. Ocean waves swell as they rise higher. A river swells after heavy rain. In these uses, swelling captures the sense of something expanding or growing larger, whether it's your chest filling with pride or waves building power as they roll toward shore.