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Union ○◂｜Definition｜1st｜20251119205401-00-⌔
Union (set theory) - Wikipedia
Union (set theory)
In set theory, the union (denoted by ∪) of a collection of sets is the set of all elements in the collection.1 It is one of the fundamental operations through which sets can be combined and related to each other. A nullary union refers to a union of zero ( ) sets and it is by definition equal to the empty set.
For explanation of the symbols used in this article, refer to the table of mathematical symbols.
Printed 2026-06-28.
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Link to original Footnotes
Weisstein, Eric W. “Union”. Wolfram Mathworld. Archived from the original on 2009-02-07. Retrieved 2009-07-14. ↩
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