The Full name for the U.K. which as it's name implies, is a combination of Great Britain (Wales, England, Scotland) and Northern Island.

The formal term for the UK.

4th richest economy of the world. Fist steps to form were re-union of England and Wales (1282). Union of afore-mentioned and Scotland (1705). This made it the United Kingdom. When it conquered Ireland/Eire, it became the United Kingdom of Great Britain and Ireland. After this hold over Ireland was minimised to six counties, it assumed the current name.