Ordinals and topological space.
55978
Prove that for every countable ordinal $\alpha$, $\alpha\times[0,1)$ is order isomoprhic to $[0,1)$
120685
Topology induced from Kuratowski Closure properties
24050
Characterization of the Closure of a Set
83166
Homeomorphism(topological spaces) version of Cantor–Bernstein–Schroeder theorem
150796
Subspace topology and order topology (2)
113688
Is Topological Space a Metric Space?
144731
Disjoint closed sets in a second countable zero-dimensional space can be separated by a clopen set
149980
Are there any countable Hausdorff connected spaces?
127900
Interior of closure of open set in topological space
34964
Recursive representation of closed sets in Baire Space ($\Sigma^1_1$)
142045
What's the definition of limit of sets(esp. ordinals) in set theory?
154474
Image of countable and uncountable sets
147961
Characterizing simply connected spaces
63489
The class of cardinal numbers is well ordered
56646
Arithmetic progression topology
70049
Irreducible topological spaces and irreducible Hausdorff space
137621
The Number of Topologies on a Finite Set