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

(1)

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

			(2)
			(3)

so

			(4)
			(5)

REFERENCES:

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