In the mathematics|mathematical area of graph theory, a graph is chordal if each of its cycle (graph theory)|cycles of four or more node (graph theory)|nodes has a chord, which is an edge (graph theory)|edge joining two nodes that are not adjacent in the cycle.
An equivalent definition is that any chordless cycle has at most three nodes. In other words, a chordal graph is a graph with no induced cycles of length more than three.
Chordal graphs are a subset of perfect graphs. They are sometimes also called rigid circuit graphs or triangulated graphs. (The latter term is sometimes erroneously used for plane triangulations; see Planar graph#Maximal planar graphs|maximal planar graphs.)