\sqcupThe \sqcup symbol represents the disjoint union operator in set theory. It is used to denote the union of two sets that are disjoint, meaning they have no elements in common.
Disjoint union of sets A and B
A \sqcup BDisjoint union of multiple sets X, Y, and Z
X \sqcup Y \sqcup ZDisjoint union of a collection of sets A_i indexed by i from 1 to n
\bigsqcup_{i=1}^{n} A_i