In mathematics, a disjoint union of a family of sets {\displaystyle } is a set A, {\displaystyle A,} often denoted by ⨆ i ∈ I A i, {\textstyle \bigsqcup _{i\in I}A_{i},} with an injection of each A i {\displaystyle A_{i}} into A, {\displaystyle A,} such that the images of these injections form a partition of A {\displaystyle A}. Wikipedia