ThmDex – An index of mathematical definitions, results, and conjectures.
Formulation F2704 on D1945: Closure point
F2704
Formulation 1
Let $T = (X, \mathcal{T})$ be a D1106: Topological space such that
(i) $E \subseteq X$ is a D78: Subset
A D2218: Set element $x \in X$ is a closure point of $E$ in $T$ if and only if \begin{equation} \forall \, U \in \mathcal{T} \, (x \in U \quad \implies \quad \exists \, y \in X : y \in E \cap U) \end{equation}