Empirical niche breadth measures were formulated based on the proportional speciesperformance over the resource states along a single niche dimension. In this paper,nichebreadth is defined as the fitness between species performance,either proportional or not,andthe distribution of sampling unit frequencies over the compartments of the n-dimensinal nichespace.An index is derived to measure this based on minimum discrimination informationstatistic. An example is presented using survey data of species and soil ...