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The United Kingdom is in the news even more than usual these days as it hurtles towards Brexit, its withdrawal from the European Union. Now scheduled to occur on October 31 at the latest, this action will either — depending on your politics and whose projections you believe — free the country from onerous servitude to foreigners and let it flourish as never before or lead to its ultimate destruction.

But what entity is on the road to secession? England? Britain? Great Britain? The United Kingdom? The British Isles? All of the above? And, anyway, what’s the difference between all these various terms, which are often used more or less interchangeably?

England is easy. It’s a country within the United Kingdom — the largest country, and the home of the U.K.’s political, financial, and cultural capital, London. Calling the entire United Kingdom “England,’ which is not uncommon, is analogous to the way people used to refer to the U.S.S.R. (Union of Soviet Socialist Republics) as “Russia.” (Both are synecdoche, a figure of speech by which the whole is referred to as one of its parts — like calling your car your “wheels.”)

Britain or Great Britain is not a country — it’s a landmass, encompassing England, Scotland, and Wales, as well as the culturally distinct county of Cornwall, which many believe should be recognized as a country just like Wales, or at least as a duchy.

Why is Britain sometimes called “Great?” The Scots like to say that England and Wales are Britain and the agglomeration became Great only when Scotland was joined to them politically in 1707. This distinction may become particularly vital in the coming years if Scotland declares its independence from the post-Brexit U.K., as many believe it will.

Other theories hold that the “Great” is to distinguish it from the similar-sounding French territory of Brittany, or because King James I wanted to make clear that he was the ruler of a greater kingdom than just the former Roman Britain.

The correct name for the sovereign nation that encompasses England, Scotland, Wales, and also Northern Ireland is the United Kingdom or U.K. Its full name is the United Kingdom of Great Britain and Northern Ireland. That’s the entity that is likely about to pull out of the European Union (with or without Scotland).

The British Isles is a geographical term that includes Great Britain, the entire island of Ireland (included in the phrase much to the dismay of the Irish), the Isle of Man, the Isles of Scilly, the Channel Islands (Jersey, Guernsey, etc.), and more than 6,000 tiny specks of land in the vicinity.

Even though the people living in the British Isles or the U.K. speak English, the meaning of many words from from one place to another. It gets even more confusing when a person from the United States tries to understand what is being said. Here are 50 British words and phrases Americans just don’t get.