a country in northwest Europe, officially called the United Kingdom of Great Britain and Northern Ireland, made up of England, Wales, Scotland, and Northern Ireland. Population: 58,789,194 (2001). Capital: London. The name "United Kingdom" was first used in 1707, when the parliaments of England and Scotland united to form one country. The country's government consists of a Queen or King, a Prime Minister, and two Houses of Parliament, the House of Commons and the House of Lords. The United Kingdom has been a member of the EU since 1972.