A shirt is a piece of clothing worn on the upper body, typically with a collar, sleeves, and buttons down the front. When you get dressed in the morning, you might pull on a T-shirt, button up a dress shirt, or slip into a polo shirt.

The word covers many styles. A dress shirt with long sleeves and buttons might be what you wear to a wedding or school concert. A T-shirt is casual and comfortable, perfect for playing outside or doing homework. A polo shirt falls somewhere in between, with a collar and a few buttons at the neck.

People have worn shirts for centuries, though they looked quite different in the past. In medieval Europe, a shirt was an undergarment worn beneath other clothes. Over time, shirts became acceptable outer clothing, and now they're one of the most common garments in the world.

The phrase keep your shirt on means to stay calm and patient, as if someone getting angry might literally tear their shirt off in frustration. If you give someone the shirt off your back, you're being extremely generous, willing to help even at personal cost. And when someone loses their shirt in a bad investment, they've lost almost everything they had.