# Definition:Disjoint Union (Set Theory)/Also known as

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## Disjoint Union: Also known as

A **disjoint union** in the context of set theory is also called a **discriminated union**.

In Georg Cantor's original words:

*We denote the uniting of many aggregates $M, N, P, \ldots$, which have no common elements, into a single aggregate by*- $\tuple {M, N, P, \ldots}$.

*The elements in this aggregate are, therefore, the elements of $M$, of $N$, of $P$, $\ldots$, taken together.*

## Sources

- 1915: Georg Cantor:
*Contributions to the Founding of the Theory of Transfinite Numbers*... (previous) ... (next): First Article: $\S 1$: The Conception of Power or Cardinal Number: $(2)$