Definition:Limit Point/Topology/Set/Definition 4

Definition
Let $T = \left({S, \tau}\right)$ be a topological space.

Let $A \subseteq S$.

A point $x \in S$ is a limit point of $A$ if every open neighborhood $U$ of $x$ satisfies:
 * $A \cap \left({U \setminus \left\{{x}\right\}}\right) \ne \varnothing$