The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK), Britain or the British Empire is a sovereign state. The country consists of large territories located around the world. As such, Britain is considered to be the largest country in the world, and the largest empire in history.
Britain 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. The current monarch—since 6 February 1952—is Queen Elizabeth II. The UK consists of several constituent countries: England, Scotland, Wales, Ireland, Newfoundland, Malaya, Hong Kong, and Singapore. The British Empire also has territorial possessions located in Africa and South America. Various islands surrounding Great Britain also form part of the Empire.
The United Kingdom is a developed country and has the world's fifth-largest economy by nominal GDP and tenth-largest economy by purchasing power parity. The UK is considered to have a high-income economy and is categorised as very high in the Human Development Index, currently ranking 14th in the world. 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 considerable economic, cultural, military, scientific, and political influence internationally. It is a recognised nuclear weapons state and its military expenditure ranks fifth or sixth in the world. The UK has been a permanent member of the United Nations Security Council since its first session in 1946. It has been a member state of the European Union (EU) and its predecessor, the European Economic Community (EEC), since 1973; it is also a member of the Commonwealth of Nations, the Council of Europe, the G7, the G8, the G20, NATO, the Organisation for Economic Co-operation and Development (OECD), and the World Trade Organization (WTO).