Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of 209,331 km2, it is the largest of the British Isles, the largest European island, the ninth-largest island in the world. In 2011, Great Britain had a population of about 61 million people, making it the world's third-most populous island after Java in Indonesia and Honshu in Japan; the island of Ireland is situated to the west of Great Britain, together these islands, along with over 1,000 smaller surrounding islands, form the British Isles archipelago. The island is dominated by a maritime climate with quite narrow temperature differences between seasons. Politically, Great Britain is part of the United Kingdom of Great Britain and Northern Ireland, constitutes most of its territory. Most of England and Wales are on the island; the term "Great Britain" is used to include the whole of England and Wales including their component adjoining islands. A single Kingdom of Great Britain resulted from the union of the Kingdom of England and the Kingdom of Scotland by the 1707 Acts of Union.
In 1801, Great Britain united with the neighbouring Kingdom of Ireland, forming the United Kingdom of Great Britain and Ireland, renamed the "United Kingdom of Great Britain and Northern Ireland" after the Irish Free State seceded in 1922. The archipelago has been referred to by a single name for over 2000 years: the term'British Isles' derives from terms used by classical geographers to describe this island group. By 50 BC Greek geographers were using equivalents of Prettanikē as a collective name for the British Isles. However, with the Roman conquest of Britain the Latin term Britannia was used for the island of Great Britain, Roman-occupied Britain south of Caledonia; the earliest known name for Great Britain is Albion or insula Albionum, from either the Latin albus meaning "white" or the "island of the Albiones". The oldest mention of terms related to Great Britain was by Aristotle, or by Pseudo-Aristotle, in his text On the Universe, Vol. III. To quote his works, "There are two large islands in it, called the British Isles and Ierne".
Pliny the Elder in his Natural History records of Great Britain: "Its former name was Albion. Old French Bretaigne and Middle English Bretayne, Breteyne; the French form replaced the Old English Breoton, Bryten, Breten. Britannia was used by the Romans from the 1st century BC for the British Isles taken together, it is derived from the travel writings of the Pytheas around 320 BC, which described various islands in the North Atlantic as far north as Thule. Marcian of Heraclea, in his Periplus maris exteri, described the island group as αἱ Πρεττανικαὶ νῆσοι; the peoples of these islands of Prettanike were called the Priteni or Pretani. Priteni is the source of the Welsh language term Prydain, which has the same source as the Goidelic term Cruithne used to refer to the early Brythonic-speaking inhabitants of Ireland; the latter were called Picts or Caledonians by the Romans. Greek historians Diodorus of Sicily and Strabo preserved variants of Prettanike from the work of Greek explorer Pytheas of Massalia, who travelled from his home in Hellenistic southern Gaul to Britain in the 4th century BC.
The term used by Pytheas may derive from a Celtic word meaning "the painted ones" or "the tattooed folk" in reference to body decorations. The Greco-Egyptian scientist Ptolemy referred to the larger island as great Britain and to Ireland as little Britain in his work Almagest. In his work, Geography, he gave the islands the names Alwion and Mona, suggesting these may have been the names of the individual islands not known to him at the time of writing Almagest; the name Albion appears to have fallen out of use sometime after the Roman conquest of Britain, after which Britain became the more commonplace name for the island. After the Anglo-Saxon period, Britain was used as a historical term only. Geoffrey of Monmouth in his pseudohistorical Historia Regum Britanniae refers to the island as Britannia major, to distinguish it from Britannia minor, the continental region which approximates to modern Brittany, settled in the fifth and sixth centuries by migrants from Britain; the term Great Britain was first used in 1474, in the instrument drawing up the proposal for a marriage between Cecily the daughter of Edward IV of England, James the son of James III of Scotland, which described it as "this Nobill Isle, callit Gret Britanee".
It was used again in 1604, when King James VI and I styled himself "King of Great Brittaine and Ireland". Great Britain refers geographically to the island of Great Britain, it is often used to refer politically to the whole of England and Wales, including their smaller off shore islands. While it is sometimes used to refer to the whole of the United Kingdom, including Northern Ireland, this is not correct. Britain can refer to either all island
The United Kingdom the United Kingdom of Great Britain and Northern Ireland, sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world; the Irish Sea lies between Great Ireland. With an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world, it is the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017. The UK is constitutional monarchy; the current monarch is Queen Elizabeth II, who has reigned since 1952, making her the longest-serving current head of state.
The United Kingdom's capital and largest city is London, a global city and financial centre with an urban area population of 10.3 million. Other major urban areas in the UK include Greater Manchester, the West Midlands and West Yorkshire conurbations, Greater Glasgow and the Liverpool Built-up Area; the United Kingdom consists of four constituent countries: England, Scotland and Northern Ireland. Their capitals are London, Edinburgh and Belfast, respectively. Apart from England, the countries have their own devolved governments, each with varying powers, but such power is delegated by the Parliament of the United Kingdom, which may enact laws unilaterally altering or abolishing devolution; the nearby Isle of Man, Bailiwick of Guernsey and Bailiwick of Jersey are not part of the UK, being Crown dependencies with the British Government responsible for defence and international representation. The medieval conquest and subsequent annexation of Wales by the Kingdom of England, followed by the union between England and Scotland in 1707 to form the Kingdom of Great Britain, the union in 1801 of Great Britain with the Kingdom of Ireland created the United Kingdom of Great Britain and Ireland.
Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain and Northern Ireland. There are fourteen British Overseas Territories, the remnants of the British Empire which, at its height in the 1920s, encompassed a quarter of the world's land mass and was the largest empire in history. British influence can be observed in the language and political systems of many of its former colonies; the United Kingdom is a developed country and has the world's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity. It has a high-income economy and has a high Human Development Index rating, ranking 14th in the world, it was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power, with considerable economic, military and political influence internationally, it is sixth in military expenditure in the world. 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 and its predecessor, the European Economic Community, since 1973. The United Kingdom is a member of the Commonwealth of Nations, the Council of Europe, the G7, the G20, NATO, the Organisation for Economic Co-operation and Development and the World Trade Organization; the 1707 Acts of Union declared that the kingdoms of England and Scotland were "United into One Kingdom by the Name of Great Britain". The term "United Kingdom" has been used as a description for the former kingdom of Great Britain, although its official name from 1707 to 1800 was "Great Britain"; the 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 was changed to the "United Kingdom of Great Britain and Northern Ireland".
Although the United Kingdom is a sovereign country, Scotland and Northern Ireland are widely referred to as countries. The UK 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 refer to Scotland and Northern Ireland as "regions". Northern Ireland is referred to as a "province". With regard to Northern Ireland, the descriptive name used "can be controversial, with the choice revealing one's political preferences"; the term "Great Britain" conventionally refers to the island of Great Britain, or politically to England and Wales in combination. However, it is sometimes used as a loose synonym for the United Kingdom as a whole; the term "Britain" is used both as a synonym for Great Britain, as a synonym for the United Kingdom. Usage is mixed, with the BBC preferring to use Britain as shorthand only for Great Britain and the UK Government, while accepting that both terms refer to the United K