England, Scotland, Wales and Northern Ireland, with a side order of the Bailiwick of the Channel Islands and the Isle of Man.
Or was it a philosophical question?
Great Britain is the largest island in the British Isles, and includes Scotland, England and Wales. The British Isles are all the islands in GB and Ireland which are separated from mainland Europe by the North Sea and The English Channel. The United Kingdom is the British Isles, without Ireland, but including Northern Ireland. Its official name is the United Kingdon of Great Britain and Northern Ireland.