A t-shirt is a casual wear usually made of cotton and polyester. It is the type of lightweight shirt without a button and it has short sleeves with a round neckline known as crewneck. T-shirts are the only piece of clothing that can be worn on any occasion. The short sleeve t-shirt can be wear under a shirt, in a suit, in the gym, on the beach, etc. The t-shirt is the most worn item other than boxers and socks.