The U.K. can also refer to the United Kingdom or simply Britain. It is a sovereign country that consists of England, Scotland, Wales, and Northern Ireland. The term Great Britain can be used interchangeably with U.K., but it only applies to the mainland and does not include Northern Ireland. Another synonym for the U.K. is the British Isles, which also includes the Republic of Ireland. It is important to note that the terms England and Britain are not interchangeable, as England refers to only one part of the U.K., while Britain refers to the whole country.