# Definition:Closed Set/Metric Space

< Definition:Closed Set(Redirected from Definition:Closed Set (Metric Space))

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## Definition

Let $M = \left({A, d}\right)$ be a metric space.

Let $H \subseteq A$.

### Definition 1

**$H$ is closed (in $M$)** if and only if its complement $A \setminus H$ is open in $M$.

### Definition 2

**$H$ is closed (in $M$)** if and only if every limit point of $H$ is also a point of $H$.