The United Kingdom of Great Britain and Northern Ireland (commonly known as the United Kingdom, the UK or Britain) is a sovereign state located off the north-western coast of continental Europe. The country includes the island of Great Britain, 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 sovereign state—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 United Kingdom is a unitary state governed under a constitutional monarchy and a parliamentary system, with its seat of government in the capital city of London. It is a country in its own right and consists of four countries: England, Northern Ireland, Scotland and Wales. There are three devolved national administrations, each with varying powers, based in Belfast, Cardiff and Edinburgh, the capitals of Northern Ireland, Wales and Scotland respectively. Associated with the UK, but not constitutionally part of it, are three Crown Dependencies. The United Kingdom has fourteen overseas territories. These are remnants of the British Empire which, at its height in 1922, encompassed almost a third of the world's land surface and was the largest empire in history. British influence can still be observed in the language, culture and legal systems of many of its former territories.
The UK is a developed country and has the world's sixth-largest economy by nominal GDP and seventh-largest economy by purchasing power parity. It was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power with leading economic, cultural, military, scientific and political influence. It is a recognised nuclear weapons state and its military expenditure ranks third or fourth in the world. The UK has been a permanent member of the United Nations Security Council since its first session in 1946; it is also a member of the Commonwealth of Nations, the Council of Europe, the G7, the G8, the G20, NATO, the OECD and the World Trade Organization.