Following the partition of Ireland and the independence of the Irish Free State in 1922, which left Northern Ireland as the only part of the island of Ireland within the United Kingdom, the name "United Kingdom of Great Britain and Northern Ireland" was adopted.Although the United Kingdom, as a sovereign state, is a country, England, Scotland, Wales and, to a lesser degree, Northern Ireland, are also regarded as countries, though they are not sovereign states.
The UK is also a member of the Commonwealth of Nations, the Council of Europe, the G7 finance ministers, the G7 forum, the G20, NATO, the Organisation for Economic Co-operation and Development (OECD), and the World Trade Organization (WTO).
The 1707 Acts of Union declared that the kingdoms of England and Scotland were "United into One Kingdom by the Name of Great Britain", though the new state is also referred to in the Acts as the "Kingdom of Great Britain", "United Kingdom of Great Britain" and "United Kingdom".
The Roman conquest, beginning in 43 AD, and the 400-year rule of southern Britain, was followed by an invasion by Germanic Anglo-Saxon settlers, reducing the Brythonic area mainly to what was to become Wales, the Brittonic Kingdom incorporating later Brittany, Dumnonia (later becomin English counties Cornwall and Devon) and the historic Kingdom of Strathclyde.
In 1066, the Normans and their Breton allies invaded England from northern France and after its conquest, seized large parts of Wales, conquered much of Ireland and were invited to settle in Scotland, bringing to each country feudalism on the Northern French model and Norman-French culture.
Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to its east, the English Channel to its south and the Celtic Sea to its south-south-west, giving it the 12th-longest coastline in the world.