Heterogeneity in an undirected network: Definition and measurement

Although heterogeneous networks are ubiquitous, a precise definition is lacking, in our opinion. We submit a definition of network heterogeneity and elaborate on a resulting approach to its measurement. This measure is denoted as HE. As an illustration HE is applied to examples from the fields of informetrics and neurosciences. Yet, it is pointed out that our definition has universal applicability.