- A set is a collection of elements in which there are no duplicates.
- The union of sets A and B (
A ∪ Bor
A + B) is the set of all elements that are contained in either A or B (or both). Note that the result is still a set (no duplicates) even if an element is in both A and B. Union is commutative, meaning
A ∪ B == B ∪ A.