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Euler diagram of the terminology of the British Isles
(lemmy.sdf.org)
Apologies. This might not be the perfect community for the post.
Which on the diagram is coterminous with “Ireland (state)”?
Exactly - that's it's proper name and how it's distinguished from Northern Ireland since they share the land mass of Ireland
You did a great job on this though, OP. It's difficult to explain to non-nationals with no idea of the history, so this is very helpful