*Definition [#x8118cd4]
Let N be a subset family of a topologcal space X.
N is called a network of X if for every point x in X and every open set U, there exists some member V in N such that $x\in V\subset U$.
*Remark [#g5d3932a]
If N consists of open sets, N is called a base.
*Reference [#c1e37387]
S. Geschke, ''Applications of elementary submodels in general topology'', Foundations of the Formal Sciences, May 7-9, 1999, p.13-20