Circle graph

For the chart, see Pie chart.
For other diagrams, see Circle diagram, Smith chart, and Nyquist plot.
A circle with five chords and the corresponding circle graph.

In graph theory, a circle graph is the intersection graph of a chord diagram. That is, it is an undirected graph whose vertices can be associated with a finite system of chords of a circle such that two vertices are adjacent if and only if the corresponding chords cross each other.