A T-shirt, or tee shirt, is a style of fabric shirt named after the T shape of its body and sleeves. Traditionally, it has short sleeves and a round neckline, known as a crew neck, which lacks a collar. T-shirts are generally made of a stretchy, light and inexpensive fabric and are easy to clean. The T-shirt evolved from undergarments used in the 19th century and, in the mid-20th century, transitioned from undergarment to general-use casual clothing.