A national flag is a flag that represents and symbolizes a sovereign state. It is flown by the government of that nation, but usually can also be flown by its citizens. A national flag is typically designed with specific meanings for its colours and symbols, which may also be used separately from the flag as a symbol of the nation. The design of a national flag is sometimes altered after the occurrence of important historical events.
The national flag is often, but not always, mentioned or described in a country's constitution, but its detailed description may be delegated to a flag law passed by the legislative, or even secondary legislation or in monarchies a decree