The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a sovereign state in Europe. Lying off the north-western coast of the European mainland, it includes the island of Great Britain—a term also applied loosely to refer to the whole country—the north-eastern part of the island of Ireland and many smaller islands. Northern Ireland is the only part of the UK that shares a land border with another state—the Republic of Ireland. Apart from this land border, the UK is surrounded by the Atlantic Ocean, with the North Sea to its east, the English Channel to its south and the Celtic Sea to its south-southwest. The country has an area of 93,800 square miles (243,000 km²).
The United Kingdom has an estimated 64.5 million inhabitants. It is a constitutional monarchy with a parliamentary system of governance. Its capital city is London, an important global city and financial centre with an urban population of 10,310,000, the fourth-largest in Europe and second-largest in the European Union. The current monarch—since 6 February 1952—is Queen Elizabeth II. The UK consists of four countries: England, Scotland, Wales, and Northern Ireland. The latter three have devolved administrations, each with varying powers, based in their capitals, Edinburgh, Cardiff, and Belfast, respectively. The nearby Isle of Man, Bailiwick of Guernsey and Bailiwick of Jersey are not part of the United Kingdom, being Crown dependencies with the British Government responsible for defence and international representation.
British influence can be observed in the language, culture, and legal systems of many of its former colonies.