A tennis shirt or also commonly known as a polo shirt or a golf shirt, is a type of t-shirt with a collar, typically with some buttons down a slit below the collar, two small slits on the bottom of either side, and an optional pocket. These shirts are usually made of knitted cloth especially pique cotton or, less commonly, silk, merino wool, or synthetic fibers.

It was a Frenchman called Rene Lacoste, a 7-time tennis Grand Slam winner, who first created the tennis shirt. He thought of bringing changes in tennis apparel because during the nineteenth to early twentieth century, tennis players were wearing long-sleeved shirts, trousers and ties to the court. These type of attire were more suitable for people working in the office as the dress shirts were simply too stiff and the ties too heavy. Lacoste's design, named after himself, comprised of a thick collar, a loose non-starched pique cotton shirt with side slits at the bottom, a longer shirt-tail at the back. The main reason to have an easily upturnable collar that was thicker than the shirt was to protect the tennis player's neck from sun burns. The interesting thing was the polo players had already been using this design since the late nineteenth century. Before Lacoste's tennis shirt design made its debut in 1929, polo players were wearing thick Oxford-cloth cotton made long-sleeved shirts and button-down collar. Although the collar design kept the wind from constantly flapping it, the polo shirt then was generally inconvenient to wear. Therefore when they discovered Lacoste's line of tennis shirts in the 1930s, they did not hesitate to adopt his design.

Soon, the polo shirt and tennis shirt were considered the one and the same. In the US, the two terms were very commonly used interchangeably in the 1950s to describe this very popular apparel. It was so popular that the tennis players openly refer to their shirt as a ?polo shirt?, even though the t-shirt was first used in tennis and even though polo only adopted it many years later.

In 1967, the popularity of polo shirts sky-rocketed when Ralph Lauren incorporated polo shirts as a leading product into his original clothing line called Polo. Though this type of shirts were not designed to wear for polo games, Lauren's polo shirts were a good imitation of the then formal polo attire.

As golf attire become more easygoing and less formal in the twentieth century, golf also adopted tennis shirt as its standard attire. Most golfers today, male and female alike, are wearing tennis shirts. For the ladies, tennis shirts can be custom made in different kinds of colors. But because golf is an entirely different game from tennis, it requires different design of cuts on the tennis shirt, resulting in the monicker ?golf shirt?. Now that tennis shirt is so commonly worn in today's society, it has its own niche in the market. Since both men and women wear it in any and every occasion, almost every fashion producer started to invent at least a version or variation of Lacoste's tennis shirt for non-athletics purposes. At the same time, tennis shirts are just the perfect substitute attire for jobs where round collar-t-shirts are deemed unacceptable and yet formal business wear is deemed overdressed, such as for semi-professional and retail workers. Tennis shirts are widely accepted as smart and casual wear.

For those who work under the sun, a tennis shirt is very suitable to wear to work because of its rough and ready style. Then in the 1990s, the high tech industry accepted tennis shirts as its standard uniform. Slowly, other industries also did the same. In order to create a more corporate look, a company logo is usually added on the front of the tennis shirt. In India, some government officials simply wear tennis shirts to work.

Tennis shirts are without doubt very fashionable in sports. Officials such as caddies, some retired golf professionals, umpires and sports announcers wear tennis shirts on a regular basis. Besides that, tennis shirts are also popular in many schools, especially junior schools. Both boys and girls wear tennis shirts as part of their compulsory uniform to schools. Because tennis shirts are closely associated with sports, they come in all sorts of light colors. The most typical color is white.

Like in the original Lacoste's design, sometimes a tennis shirt is cut so that the back hangs a few centimeters lower than the front also known as a "tennis tail". The longer tail is meant to keep the shirt tucked into the back of a man's tennis shorts when he is bent over to survey the court. The easily-upturnable collar remains another athletic aid to protect against sun burns.

The evolution of the tennis shirt or the polo shirt will be forever changing with the times. But no matter how much it changes, it will have its own category of clothing.