The United Kingdom of Great Britain and Northern Ireland (also known as the United Kingdom, the U.K., or Britain) is a country to the north-west of mainland Europe. It comprises the island of Great Britain, the north-east part of the island of Ireland and many small local islands. Northern Ireland is the only part of the UK with a land border, sharing it with the Republic of Ireland. Apart from this land border, the UK is surrounded by the Atlantic Ocean, the North Sea, the English Channel and the Irish Sea. The largest island, Great Britain, is linked to France by the Channel Tunnel. --------------------------- The United Kingdom is a parliamentary democracy and a constitutional monarchy comprising four constituent countries — England, Northern Ireland, Scotland and Wales — with Elizabeth II as head of state. The Crown Dependencies of the Channel Islands and the Isle of Man, formally possessions of the Crown, are not part of the UK but form a federation with it.The UK has fourteen overseas territories,all remnants of the British Empire, which at its height encompassed almost a quarter of the world's land surface. It is a highly developed country, with the fifth-largest economy in the world. --------------------------------- Britain was the world's foremost power during the 19th and early 20th century, but the economic cost of two world wars and the decline of its empire in the latter half of the 20th century diminished its leading role in global affairs. The UK nevertheless retains major economic, cultural, military and political influence today and is a nuclear power, with the second highest defence spending in the world. It holds a permanent seat on the United Nations Security Council, and is a member of the G8, NATO, the European Union and the Commonwealth of Nations.