This Venn Diagram 2 Union Circle is a diagram that shows the relationships between two sets. The circles are divided into four parts. The first and second parts represent the sets. The third and fourth parts represent the union of those two sets. This Venn Diagram 2 Union Circle is a diagram that shows the relationships between two sets. The circles are divided into four parts. The first and second parts represent the sets. The third and fourth parts represent the union of those two sets.