The United Kingdom of Great Britain and Northern Ireland (usually shortened to the United Kingdom, the U.K., or Britain) is a country and sovereign state that lies to the northwest of mainland Europe, with its only land border with the Republic of Ireland. It extends over all of the island of Great Britain and the northeast part of the island of Ireland.
The United Kingdom is bounded by the Atlantic Ocean, and its ancillary bodies of water, including the North Sea, the English Channel, the Celtic Sea, St George’s Channel and the Irish Sea. The United Kingdom is linked to France and continental Europe by the Channel Tunnel.
The United Kingdom is a constitutional monarchy composed of four constituent countries: England, Scotland, Wales and Northern Ireland. The current monarch is Queen Elizabeth II, who is also the Queen and Head of State of 15 other Commonwealth Realms, including Canada, Australia, New Zealand and Jamaica.
The Crown Dependencies of the Channel Islands and the Isle of Man, formally possessions of the Crown, form a federacy with the United Kingdom collectively known as the British Islands. The UK also has 14 overseas territories, all remnants of the British Empire, which at its height encompassed more than a quarter of the world’s surface and population.
Although Britain was the foremost great power during the 19th century, the economic cost of two world wars and the giving of independence to many of its empire states (including India, much of Africa, and Hong Kong) during the latter half of the 20th century diminished Britain’s status in global affairs. However, as a permanent member of the United Nations Security Council, a nuclear power, a member of the G8, the world’s fifth–largest economy, and having the second highest defense spending, Britain remains an important political, economic and military world power. It is a member of the European Union and the Commonwealth of Nations.
Ireland (Irish: Éire; Ulster Scots: Airlann) is the third–largest island in Europe and the 20th largest in the world. It lies to the northwest of continental Europe. To the east of Ireland, separated by the Irish Sea, is the island of Great Britain.
Politically, Ireland is divided into the Republic of Ireland, a sovereign state occupying five–sixths of the island, and Northern Ireland, a part of the United Kingdom, occupying the northeastern sixth of the island. The name “Ireland” derives from the name “Ériu” (in modern Irish, Éire), with the addition of the Germanic word “land.”
The population of the island is slightly under 6 million (2006), with 4,239,848 in the Republic of Ireland (1.7 million in greater Dublin) and about 1.7 million in Northern Ireland (0.6 million in greater Belfast).