Category:Systems of Open Neighborhoods

This category contains results about Systems of Open Neighborhoods.
Definitions specific to this category can be found in Definitions/Systems of Open Neighborhoods.

Let $T = \struct {S, \tau}$ be a topological space.

Let $x \in S$.

Let $\map \UU x$ be the set of all open neighborhoods of $x$ in $T$.

Then $\map \UU x$ is the system of open neighborhoods of the point $x$.