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  "body": "\n## Statement\n\nLet $X$ be a [[topological space|0CNQXVBHCX]] and let $S \\subseteq X$.\nThen the [[interior|0C38S0KMJK]] $\\operatorname{int} S$ is an [[open set|01ZQQDCERP]] of $X$.\n\n## Remarks\n\nProof: $\\operatorname{int} S$ is a union of open sets, and each union of open sets is open by the axioms of a topology.\nIt follows that $\\operatorname{int}(\\operatorname{int} S) = \\operatorname{int} S$.\n\n## Explanations\n\n### L1 human\n\nThe interior is made by putting together open sets, and open sets put together give an open set.\n",
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