Britannia
The term Britannia is, in UO, often used incorrectly as a synonym with Sosaria.
Properly, however, it refers to the original UO map, the one with the cities of Trinsic, Britain, and Yew; the Kingdom created by Lord British's consolidations of the realms found in the single-player game.
Originally, Britannia was under the political control of Lord British and his government. Then, the Lost Lands were discovered, and thus a map was introduced that had very, very little to do with Lord British.
The Lost Lands are really not controlled by anyone, though presumably town governments exist in Delucia and Papua, the 2 cities found in the Lost Lands. Whether or not those cities are under the dominion of Britannia is not clear, and is sometimes the subject of role-played player conflicts.
Now Britannia is under the control of whatever the dominant Faction is.
Britannia and The Lost Lands are located on a planet that is sometimes called Sosaria.
