Lying off the north-western coast of the European mainland, the UK includes the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands.
The term has no definite legal connotation, but is used in law to refer to United Kingdom citizenship and matters to do with nationality.
Apart from this land border, the UK 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.
The Irish Sea lies between Great Britain and Ireland.
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.
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.