In this paper we introduce the definition of n-dimensional overlap functions and we justify the axiomatization proposed in its definition. Basically, these functions allow to measure the degree of overlapping of several classes in a given classification system and for any given object. We also show a construction method for this class of functions, studying its relationships with the properties of migrativity, homogeneity and Lipschitz continuity. Finally, we propose an example where the use of n-dimensional overlap functions provides better results than those obtained with the commonly used product t-norm.