It has been a permanent member of the United Nations Security Council since its first session in 1946.
It has been a leading member state of the European Union (EU) and its predecessor, the European Economic Community (EEC), since 1973; however, a referendum in 2016 resulted in 51.9% of UK voters favouring leaving the EU, and the country's exit is being negotiated.
It has a high-income economy and has a "very high" Human Development Index, ranking 16th in the world.
The Irish Sea lies between Great Britain and Ireland.
People of the United Kingdom use a number of different terms to describe their national identity and may identify themselves as being British; or as being English, Scottish, Welsh, Northern Irish, or Irish; However, it is usually abbreviated to "DU" for the mutated form "Y Deyrnas Unedig".
In Scottish Gaelic, the long form is "Rìoghachd Aonaichte Bhreatainn is Èireann a Tuath" and the short form "Rìoghachd Aonaichte".
The term "Britain" is often used as synonym for the United Kingdom.
The term "Great Britain", by contrast, refers conventionally to the island of Great Britain, or politically to England, Scotland and Wales in combination.