The names Great Britain and United Kingdom are often used interchangeably. However, they are not actually synonymous. The reason for the two names, and the difference between them, has to do with the expansive history of the British Isles.

It is inappropriate to refer to the United Kingdom as Great Britain or England; one should be specific about toponyms (place names) and utilize the correct nomenclature. Remember, United Kingdom (or the U.K.) is the country, Great Britain is the island, and England is one of the U.K.'s four administrative regions.

In technical language, United Kingdom is a political term while Great Britain is a geographical one. However, these two terms overlap heavily in popular usage. Notably, the term Great Britain is popularly used as a synonym of United Kingdom, meaning Northern Ireland is included.

What is the difference between Great Britain and the United Kingdom? Great Britain, therefore, is a geographic term referring to the island also known simply as Britain. United Kingdom, on the other hand, is purely a political term: it’s the independent country that encompasses all of Great Britain and the region now called Northern Ireland.

The terms Britain and Great Britain are, as we said above, synonymous geographical terms referring to the largest of the islands in the British Isles. But Britain and Great Britain are also used to refer to the United Kingdom of Great Britain and Northern Ireland aka the United Kingdom aka the UK.