A T-shirt (or tee shirt) is a shirt, usually buttonless, collarless, and pocketless, with a round neck and short sleeves, that is pulled on over the head and covers most of a person's torso. There are also long-sleeved T-shirt and sleeveless T-shirt variants.
An example of a tie-dye t-shirt
The idea of the T-shirt came to the USA during WWI when US soldiers noticed the light cotton undershirts European soldiers were using while the US soldiers sweated in their wool uniforms. Since they were so much more comfortable they quickly became popular among the Americans, and because of their design they got the name T-shirt. During WWII the T-shirt had become standard issue underwear in both the U.S. Army and Navy. Although the T-shirt was formally underwear, soldiers often used it without a shirt covering it while doing heavy labor or while stationed in locations with a hot climate. As a result, the public was frequently exposed to pictures of members of the armed forces wearing pants and a T-shirt. As an example, the cover of the July 13, 1942 issue of Life magazine, features a picture of a soldier wearing a T-shirt with the text "Air corps gunnery school" ().
After WWII the T-shirt started appearing without a shirt covering it in civilian life. According to the New York Times, the 1948 presidential campaign of Thomas E. Dewey produced a "Dew It for Dewey" T-shirt, which was followed in 1952 by "I Like Ike" T-shirts in support of Dwight D. Eisenhower. John Wayne, Marlon Brando and James Dean all wore them on national TV. At first the public was shocked, but by 1955 it had become acceptable. The T-shirt became cool when James Dean wore it in the film Rebel Without a Cause.