The United Kingdom of Great Britain and Northern Ireland (usually shortened to the United Kingdom, the UK and Britain) is a country and sovereign state occupying Great Britain and the northeast of Ireland off the northwest coast of mainland Europe. Its territory and population are primarily situated on the island of Great Britain, but it also shares a land border with the Republic of Ireland on the island of Ireland. The United Kingdom is otherwise surrounded by the Atlantic Ocean and its ancillary bodies of water- the North Sea, the English Channel, the Celtic Sea, and the Irish Sea.