Etymology and terminology
1707 Acts of Union declared that the kingdoms of
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".
[note 12] The term "United Kingdom" is found in informal use during the 18th century and the country was also occasionally referred to as the "United Kingdom of Great Britain" though its full official name, from 1707 to 1800, was merely "Great Britain", without a "long form".
Acts of Union 1800 united the Kingdom of Great Britain and the
Kingdom of Ireland in 1801, forming the
United Kingdom of Great Britain and Ireland. 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.
 Scotland, Wales and Northern Ireland have devolved self-government.
 The British Prime Minister's website has used the phrase "countries within a country" to describe the United Kingdom.
 Some statistical summaries, such as those for the twelve
NUTS 1 regions of the United Kingdom, also refer to Scotland, Wales and Northern Ireland as "regions".
 Northern Ireland is also referred to as a "province".
 With regard to Northern Ireland, the descriptive name used "can be controversial, with the choice often revealing one's political preferences".
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.
 However, it is sometimes used as a loose synonym for the United Kingdom as a whole.
 GB and GBR are the
standard country codes for the United Kingdom (see
ISO 3166-2 and
ISO 3166-1 alpha-3) and are consequently used by international organisations to refer to the United Kingdom. Additionally,
the United Kingdom's Olympic team competes under the name "Great Britain" or "Team GB".
The adjective "British" is commonly used to refer to matters relating to the United Kingdom. The term has no definite legal connotation, but is used in law to refer to United Kingdom citizenship and
matters to do with nationality.
 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,
Northern Irish, or Irish;
 or as being both.
In 2006, a new design of
British passport was introduced. Its first page shows the long form name of the state in English,
 In Welsh, the long form name of the state is "Teyrnas Unedig Prydain Fawr a Gogledd Iwerddon", with "Teyrnas Unedig" being used as a short form name on government websites.
 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".