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 northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of the island of Ireland, and many small islands. <br/> The United Kingdom is a constitutional monarchy and unitary state consisting of four countries: England, Northern Ireland, Scotland and Wales. It is governed by a parliamentary system with its seat of government in London, the capital, but with three devolved national administrations of varying powers in Belfast, Cardiff and Edinburgh, the capitals of Northern Ireland, Wales and Scotland respectively. <br/> The UK is a developed country, with the world's sixth largest economy by nominal GDP and the sixth largest 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, but the economic and social 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. It is a Member State of the European Union, a permanent member of the United Nations Security Council, and is a member of the Commonwealth of Nations, G8, G20, NATO, OECD, and the World Trade Organization.