A set fixed within the framework of a theory and consisting of all objects considered in this theory.

The complement of the universal set is the empty set.

## See also

Empty Set,

Finite
Set
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## References

Fraenkel, A. A. and Bar-Hillel, Y. *Foundations of Set Theory.* Amsterdam, Netherlands, 1958.## Referenced on Wolfram|Alpha

Universal Set
## Cite this as:

Weisstein, Eric W. "Universal Set." From
*MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/UniversalSet.html

## Subject classifications