In set theory, the **union** of a collection of sets is the set of all the elements of all the sets of the collection. It is denoted as .

## Formal DefinitionEdit

Let be a set.

Let be a set.

Then, the union of and is defined as:

## See AlsoEdit

## External LinksEdit

Set Theory

**Concepts**

Set theory, Set, Element, Subset, Equality, Empty Set, Enumeration, Function, Ordered pair, Uncountable set, Extensionality, Finite set, Domain, Codomain, Image, DeMorgan's Laws

**Operations**

**Union**, Intersection, Relative complement, Absolute complement, Symmetric complement, Cartesian product, Power Set