@dplattsf @Jeffwni The You diagram is a Venn diagram. Venn diagrams are a subset of Euler diagrams. All possible overlaps must be covered, so typically they are drawn as 2, 3 or 4 overlapping circles (theoretically other shapes could be used). The diagram in the background of the xkcd comic is an Euler diagram that is not a Venn diagram - not all circles overlap each other.