Disjoint Union -- from Wolfram MathWorld

Foundations of Mathematics > Set Theory > Set Operations >

Disjoint Union

The disjoint union of two sets and is a binary operator that combines all distinct elements of a pair of given sets, while retaining the original set membership as a distinguishing characteristic of the union set. The disjoint union is denoted

$A union ^*B=(A×{0}) union (B×{1})=A^* union B^*,$

(1)

where is a set direct product. For example, the disjoint union of sets and can be computed by finding

			(2)
			(3)

			(4)
			(5)

REFERENCES:

Armstrong, M. A. Basic Topology, rev. ed. New York: Springer-Verlag, 1997.

CITE THIS AS:

Weisstein, Eric W. "Disjoint Union." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/DisjointUnion.html