Is it true that every closed set is a countable intersection of open intervals?
44623
Closed set as a countable intersection of open sets
10127
Example of a sequence of closed and connected sets whose intersection is disconnected
156520
Intervals are connected and the only connected sets in $\mathbb{R}$
128844
An empty intersection of decreasing sequence of closed sets
125580
Proving that every countable metric space is disconnected?
121366
Intervals and cardinality
63276
Is an arbitrary union of a chain of countable sets countable?
149317
An open subset of $\mathbb{R}$ is an at-most-countable union of disjoint open intervals
148507
Why an open set in $R^n$ might not be written as countable union of disjoint open intervals?
127575
Prove that Open Sets in $\mathbb{R}$ are The Disjoint Union of Open Intervals Without the Axioms of Choice
24050
Characterization of the Closure of a Set
99464
Proof Concerning Indexed family of Sets and Intervals
12472
Let $X$ and $Y$ be countable sets. Then $X\cup Y$ is countable
35692
The set of all finite subsets of the natural numbers is countable
99678
Is a sphere a closed set?
119649
Every metrizable space with a countable dense subset has a countable basis
102543
Real definition of "countable set"