Functional diversity can be quantified using one single trait at a time or multiple traits (see the descriptions of multiple-indices in other page). There are single trait metrics that include abundance (e.g. number of individuals per species, relative basal area per especie) to weight the relative contribution of species to the index. Some single-trait metrics are the Community Weighted Mean (CWM), functional divergence (FDvar) and functional regularity index (FRO).