ThmDex – An index of mathematical definitions, results, and conjectures.
Formulation F234 on D1945: Closure point
F234
Formulation 0
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 E \cap U \neq \emptyset) \end{equation}