How is the Cofinite Topology on an infinite set even possible?
88823
How can the empty set be open in the definition of the cofinite topology?
91163
Let the set S be infinite, and the set T countably infinite. Show that S and S U T have the same cardinality
134071
If A is a finite set and B is an infinite set, then B\A is an infinite set
146560
Is there any uncountably infinite set that does not generate the reals?
148927
Why does every countable limit ordinal have cofinality $\omega$?
78513
Show finite complement topology is, in fact, a topology
97064
Dense set in an infinite cofinite space
70940
Homework - set theory infinite union
151950
Why is indiscrete topology unmetrizable?
127200
Are there fields and ordered fields of every infinite cardinality?
66398
Union of a finite set and a countably infinite set is countably infinite
33157
Proof that an infinite subset of $\mathbb{N}$ is countable
77548
Given an arbitrary infinite set $S$, how to construct an injection $\mathbb{N} \to S$ with the Axiom of Choice?
109374
Is the Discrete Topology on $X$ the Only One Containing All Infinite Subsets of $X$?
130361
Basis for a topology with a countable number of sets
24372
Infinite Set is Disjoint Union of Two Infinite Sets
156006
Cardinality of set containing all infinite subsets of $\mathbb{Q}$