The United Kingdom is officially called the United Kingdom of Great Britain and Northern Ireland. It is a sovereign state, and consists of four countries: England, Northern Ireland, Scotland, and Wales. It is also called Great Britain, but strictly speaking Great Britain is the geographic part of the UK excluding Northern Ireland. England was first consolidated in 945 CE, combined with Wales in the 13th century to form Britain, and in 1707 combined with Scotland, to form the Kingdom of Great Britain. In 1800 this merged with Ireland to form the UK, but in 1922 the southern portion of Ireland became independent. The UK is now a parliamentary democracy.
It has an area of 243,610 sq km, a population of 63.7 million, and a very high HDI of 0.875.