A graph crossing is a common point, other than a common endpoint, of the arcs representing two or more distinct edges in a drawing of a graph. In a good drawing of a graph, no three edges cross at one point, adjacent edges do not cross, and any two edges cross at most once (Schaefer 2018).
The graph crossing number minimizes the number of graph crossings over all drawings of a given graph. Restricting the drawings to straight edges instead gives the rectilinear crossing number.
