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  "body": "\n## Summary\n\nIn mathematics, the **disjoint union** (or **discriminated union**) $A \\sqcup B$ of the sets $A$ and $B$ is the set formed from the elements of $A$ and $B$ labelled (indexed) with the name of the set from which they come. So, an element belonging to both $A$ and $B$ appears twice in the disjoint union, with two different labels.\n",
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