Definition:Set Derivative

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

Let $A \subseteq S$.

The derivative of $A$ in $T$ is the set of all accumulation points of $A$.

It is usually denoted on $\mathsf{Pr} \infty \mathsf{fWiki}$ as $A'$.

Also known as

The set derivative can also be referred to as the derived set.

It can also be denoted $\operatorname{Der} A$.