Venn diagram representing the union of two sets A and B.

- When the intersection of two sets is empty, the sets are said to be disjoint.
- The union of two sets A and B, symbolized by A ∪ B, is the set of all elements that are in A or B or both.
- So A ∪ B includes all of set A together with all of set B (but don't repeat elements).
- x ∈ A ∪ B means x is in A or x is in B.
- Union keyword: or
- Shade the entire area of both circles A and B in the Venn diagram, including the overlapping region.
- Example 4: A ∪ B = {1, 2, 3, 4, 5, 6, 8, 10, 12}
- Try This One (4): B ∪ C = {2, 4, 6, 8, 10, 12} ∪ {6, 7, 8, 9, 10} = {2, 4, 6, 7, 8, 9, 10, 12}