Two circles may intersect in two imaginary points, a single degenerate point, or two distinct points. The combined area of sets A and B is called the union of A and B, denoted by A ∪ B. The area in both A and B, where the two sets overlap, is called the intersection of A and B, denoted by A ∩ B. If the circles intersect in two points, the line connecting their two points of intersection is called the radical line.
In the following example, the 'radical line' would be the Assistant Director.
A Venn-like diagram to help explain film production. I like it. A lot.
Diagram courtesy On-set With An Indie Film Junkie