* Britannia: This is a more poetic or historical term, often used to refer to the Roman province or a personified representation of Great Britain.
* Great Britain: This is the full name of the island, technically a more accurate term than "Britain" alone, which can also refer to the United Kingdom.
* UK: This is a common abbreviation for the United Kingdom, which includes England, Scotland, Wales, and Northern Ireland.
It's important to consider the context and intended meaning when deciding which term to use.