Teorem: $(X,\tau)$ topolojik uzay olsun.
$$(X,\tau), \text{ normal}$$
$$\Leftrightarrow$$
$$(\forall F\in\mathcal{C}(X,\tau))[U\in\mathcal{U}(F)\Rightarrow (\exists \{W_n|n\in\mathbb{N}\}\subseteq\tau)(F\subseteq \bigcup_{n\in\mathbb{N}} W_n)(cl(W_n)\subseteq U)].$$