Sometimes flags have names. They may be official or colloquial, descriptive or shorthand. The red white and blue striped flag of France is known as the Tricolour. The flag of the United States is called the Stars and Stripes or the Star-spangled Banner, sometimes nicknamed Old Glory. The Scottish flag, the St Andrew’s cross, is known as the Saltire.
The flag of the United Kingdom is called the Union Jack. Sometimes people mistakenly say that it should be called the Union Flag, and that it can only be called the Union Jack if flown from a ship. This is incorrect. The Flag Society reported after several years of research that there is no historical evidence for such a distinction. The name of the UK flag is the Union Jack. It is not merely pedantic to insist it be called the Union Flag; it is simply wrong. The two terms were always interchangeable, from the first records of the flag when it was created in the early Seventeenth Century.
Those who reach for their pens to write to newspapers or broadcasting organizations to insist on “Union Flag” unless it is ship-borne, are fighting a lost cause. Its name is the “Union Jack,” and those who call it by this name are right to do so.