Consonance

Here is the list of posts on places where countability matters in topology, so far:

1. The Dolecki-Greco-Lechicki theorem
2. Some new, easy facts on consonant spaces
3. The Sorgenfrey line is not consonant
4. Q is not consonant: the Costantini-Watson argument
5. Strongly compact sets and the double hyperspace construction

— Jean Goubault-Larrecq