Irreducible closed subsets of an open set
99341
Basic question: closure of irreducible sets
70249
Irreducibility of Polynomials in $k[x,y]$
99236
Interior of closure of an open set
70048
In which topologies do open sets maintain open under countable or arbitrary intersection?
143105
Show that, for every real number a, the set {$x ∈ S | f(x) ≤ a$} is a closed subset of $\mathbb R^d$
99678
Is a sphere a closed set?
60424
Uncountable family of uncountable compact subsets of $\mathbb{R}$
73130
A simple question about open set
24050
Characterization of the Closure of a Set
28079
Do these definitions of irreducibility of algebraic sets coincide?
49220
Open Sets of $\mathbb{R}^1$ and axiom of choice
44673
$M$ connected $\iff$ $M$ and $\emptyset$ are the only subsets of $M$ open and closed at the same time
158569
Proving a particular subset of $R^n$ is closed
78549
Any prime is irreducible
136106
Is every open subset of $ \mathbb{R} $ uncountable?
144731
Disjoint closed sets in a second countable zero-dimensional space can be separated by a clopen set
138202
Every open set in $\mathbb{R}$ is a countable union of closed sets