# Definition:Accumulation Point/Set

## Definition

Let $\paren { S, \tau }$ be a topological space.

Let $A \subseteq S$.

Let $x \in S$.

Then $x$ is an accumulation point of $A$ if and only if:

$x \in \cl {A \setminus \set x}$

where $\operatorname{cl}$ denotes the (topological) closure of a set.

## Also see

• Results about accumulation points can be found here.