Editing Union (set theory) (section)

{{short description|Set of elements in any of some sets}}
[[File:Venn0111.svg|thumb|200px|Union of two sets:<br /><math>~A \cup B</math>]]
[[File:Venn 0111 1111.svg |thumb|200px|Union of three sets:<br /><math>~A \cup B \cup C</math>]]
[[File:Example of a non pairwise disjoint family of sets.svg|200px|thumb|The union of A, B, C, D, and E is everything except the white area.]]

In [[set theory]], the '''union''' (denoted by ∪) of a collection of [[Set (mathematics)|sets]] is the set of all [[element (set theory)|element]]s in the collection.<ref>{{cite web |author=Weisstein |first=Eric W |title=Union |url=http://mathworld.wolfram.com/Union.html |url-status=live |archive-url=https://web.archive.org/web/20090207202412/http://mathworld.wolfram.com/Union.html |archive-date=2009-02-07 |access-date=2009-07-14 |publisher=Wolfram Mathworld}}</ref> It is one of the fundamental operations through which sets can be combined and related to each other. 
A '''{{visible anchor|nullary union|Nullary union}}''' refers to a union of [[Zero|zero ({{tmath|1= 0 }})]] sets and it is by definition equal to the [[empty set]]. 

For explanation of the symbols used in this article, refer to the [[List of mathematical symbols|table of mathematical symbols]].