In this program
- Hausdorff and regular spaces
- Normal spaces (introduction)
- Urysohn lemma
- Tietze extension (as covered)
- First and second countability
Separation and countability
First and second countability
Topology · Theoretical / proof-based
Topic
First and second countability
Graduate Topology — scope drawn from Bradley–Bryson–Terilla Topology (MIT Press open chapters) and typical graduate point-set / algebraic topology intro syllabi.