Examples of Non-Hausdorff Topology
72875
"Naturally occurring" non-Hausdorff spaces?
35401
Examples of finite groups that are not a semidirect product
41872
Show that $\mathbb{R}^2$ is not homeomorphic to $\mathbb{R}^2 \setminus\{(0,0)\}$
111689
Surjective, but not injective endomorphism
147331
Compactness and Hausdorffness
17607
Open maps which are not continuous
129227
An example of neither open nor closed set
45432
Showing that $f:(0,2\pi]\to S^1$ is not a homeomorphism
62793
$\mathbb{R}$ with the lower limit topology is not second-countable
110726
Example of a non-gcd domain
83166
Homeomorphism(topological spaces) version of Cantor–Bernstein–Schroeder theorem
95897
Which sets occur as boundaries of other sets in topological spaces?
108408
Example of quotient mapping that is not open
6118
Homeomorphism of the real line-Topology
131890
Totally disconnected space that is not $T_2$
32819
Looking for examples of first countable, compact spaces which is not separable
15128
Example of non-decomposable ideal