A flag is a piece of fabric, often flown from a pole or mast, generally used symbolically for signaling or identification. It is most commonly used to symbolize a country. The term flag is also used to refer to the graphic design employed by a flag, or to its depiction in another medium.

The first flags were used to assist military coordination on battlefields, and flags have since evolved into a general tool for rudimentary signaling and identification, it was especially used in environments where communication is similarly challenging (such as the maritime environment where semaphore is used). National flags are potent patriotic symbols with varied wide-ranging interpretations, often including strong military associations due to their original and ongoing military uses. Flags are also used in messaging, advertising, or for other decorative purposes. The study of flags is known as vexillology, from the Latin vexillum meaning flag or banner.

History

The origin of modern flags lies in our remote prehistoric past. When people started to form large groups to live and hunt together, they appointed a leader to rule them and settle disputes. As a mark of office this leader would wear some sort of ceremonial head-dress and hold a long decorative staff, rod or spear, topped with an ornament or tribal emblem. The staff was also used as a visible sign to rally around, or to point out the direction of a march or attack. This prehistoric, or proto-flag, is known as a vexilloid. Later in Ancient China, a different tradition developed when silk was invented between 6000 and 3000 BC. This strong, light fabric was ideal for making banners, which were much easier to carry than the vexilloids that had been used earlier, and they were also easier to see from a distance. From Ancient China the use of fabric flags spread to Mongolia, Japan, India, Persia, Ancient Greece, and finally the Roman Empire and the rest of Europe.

The usage of flags spread from India and China, where they were almost certainly invented,flag. (2008). Encyclopædia Britannica. Chicago: Encyclopædia Britannica. to neighboring Burma, Siam, and southeastern Asia.

The Persians used Derafsh Kaviani as the flag, at the time of Achaemenian dynasty at 550–330 B.C. Afterwards it was used in different look by the late Sassanid era (224-651). It was also representative of the Sassanid state - Ērānshāhr, the "Kingdom of Iran" - and may so be considered to have been the first "national flag" of Iran.

Originally, the standards of the Roman legions were not flags, but symbols such as the eagle of Augustus Caesar's Xth legion; this graphic of the eagle would be placed on a staff for the standard-bearer to hold up during battle. But a military unit from Dacia had for a standard a dragon with a flexible tail which would move in the wind; the legions copied this, and eventually all the legions had physically flexible standards–the modern-day flag.