The

**disjoint union**of $X = \{ X_j \}_{j \in J}$ is the D11: Set \begin{equation} \coprod_{j \in J} X_j : = \bigcup_{j \in J} \{ (x, j) :x \in X_j \} \end{equation}

▾ Set of symbols

▾ Alphabet

▾ Deduction system

▾ Theory

▾ Zermelo-Fraenkel set theory

▾ Set

▾ Collection of sets

▾ Set union

▾ Alphabet

▾ Deduction system

▾ Theory

▾ Zermelo-Fraenkel set theory

▾ Set

▾ Collection of sets

▾ Set union

Dual definition

Also known as

Set coproduct