Every subspace of a separable metric space is separable — fails for general topological spaces
Counterexample
Is this true?
No — it is false.
Go deeper· Explained in full in The counterexample zoo: cofinite, cocountable, Sorgenfrey, Cantor· Asked in CSIR NET June 2024· From Topology › Standard spaces: cofinite, cocountable, Sorgenfrey, Cantor set