I'm trying to understand the relationship between the different separation axioms:
- T2 (Hausdorff): two distinct points can be separated by open sets
- Regular: a closed set and a point not in it can be separated by open sets
- Normal: two disjoint closed sets can be separated by open sets
I know that T4 (normal + T2) implies regular, so if a space is not regular, it is either not Hausdorff or not normal. I can't find out if it's possible to have a space that is regular, but not Hausdorff and not normal.