Closure
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Revision 931
8/5/2026, 7:22:26 AM · Sequoia
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The closure of a subset $A$ of a [[Topological space|topological space]] $X$ is the smallest [[Closed set|closed set]] of $X$ containing $A$, and is denoted $\overline{A}$ or $\operatorname{cl}(A)$.2
Note that $X$ is always closed, hence this definition makes sense.Revision 842
8/2/2026, 3:45:37 PM · Sequoia
Concept edited
This older revision predates detailed metadata tracking.
Revision 753
7/31/2026, 1:15:01 PM · Ancient Tree
Concept created
Recorded titleClosure
Recorded typeDefinition
The closure of a subset $A$ of a [[Topological space|topological space]] $X$ is the smallest [[Closed set|closed set]] of $X$ containing $A$, and is denoted $\overline{A}$ or $\operatorname{cl}(A)$.