Let $T = (X, \mathcal{T})$ be a
D1106: Topological space such that
A
D2218: Set element $x \in X$ is a
limit 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 \text{ and } x \neq y)
\end{equation}