A flag is a rectangular or triangular piece of cloth or paper (tied to the end of a stick, pole, etc.) used as a symbol of the state, association, body, etc. or as a sign; pennant; stump: often hoisted on a pole, generally used symbolically for signaling or identification.[1] It is often also used to symbolize a country to show its sovereignty.

Flags were first used to aid military coordination on the battlefield, and flags have since evolved to become a common tool for basic signaling and identification, especially in environments where communication is also challenging (such as maritime environments where semaphores are used). National flags are strong patriotic symbols with widely varied interpretations, often including strong military associations due to their original and continuing military nature. Flags are also used in messages, advertisements, or for other ornamental purposes. The study of flags is known as vexilology.