I was very happy to stumble upon (thanks Ed) this explanation of the terms United Kingdom, Great Britain, etc.—via a Venn diagram. The precise definitions of these terms have always confused me. It was created by Sam Hughes.
Follow the link to his page to read a more detailed discussion of the terms. My favorite line was the last one in which he wrote:
Lastly, to be pedantic, this is actually an Euler diagram, not a Venn diagram.

Thanks!
By: Chapati on February 4, 2009
at 6:32 pm
I’ve been calling EVERYTHING a Venn Diagram — I never knew that there was such a thing as an Euler Diagram. Whoa.
Sam
By: samjshah on February 4, 2009
at 7:27 pm