Must a countable set be infinite?
72007
What do finite, infinite, countable, not countable, countably infinite mean?
41192
Neatest proof that set of finite subsets is countable?
33157
Proof that an infinite subset of $\mathbb{N}$ is countable
76809
"Some" and "Any"; countables and uncountable
145428
Set $A$ is countably infinite if and only if there exists a bijection $f: \mathbb{N} \rightarrow A$
99599
Uncountable and countable
119624
A Dedekind infinite set has a countably infinite proper subset
48727
Why is the Cantor set not defined by a limit?
69838
Does a countably infinite power set exist?
84936
The set of all finite sequences of members of a countable set is also countable
127200
Are there fields and ordered fields of every infinite cardinality?
42794
Prove that functions map countable sets to countable sets
118595
Proving that a set is countable by finding a bijection
63276
Is an arbitrary union of a chain of countable sets countable?
42095
Existence in ZF of a set with countable power set
68230
The cardinality of a countable union of sets with less than continuum cardinality
52682
Is the power set of the natural numbers countable?