Britain (brĬt´ən), alternate term for Great Britain, comprised of England, Scotland, and Wales. Often used synonymously with the United Kingdom, the name Britain is derived from Britannia, given by the Romans to the portion of the island of Great Britain that they occupied. It has sometimes been used to refer to Great Britain in the period before the Germanic invasions of the 5th cent. AD After the union (1707) of England and Scotland, parliamentary legislation for a time used "South Britain" and "North Britain" to refer to the two parts. For a more complete history, see Great Britain.