of irregularity Definitions of irregularity have been important in the study of network heterogeneity, which has implications in networks found across biology, ecology, technology, and economy. There have been several graph statistics that have been suggested, many of which are based on the number of vertices in a graph and their degrees. The characterization of highly irregular graphs has also been applied to the question of heterogeneity, yet all of these fail to shed enough light on real-world situations. Efforts continue to be made to find appropriate ways to quantify network heterogeneity. References Graph families