Below is a Venn diagram of the four circles that are being discussed in this section. The first circle, "Venn Diagram 4 Union Circles", is the title of the section and has no relation to any of the other three circles. The second circle, "Venn Diagram 3 Union Circles", is where we discuss how three circles can intersect with each other. The third circle, "Union Circle 2", discusses how two circles intersect with each other. Finally, the fourth circle, "Union Circle 1", discusses how one circle intersects with another.