1. A new concept of functional abundance of species is presented. The
absolute and relative functional abundance is mainly aimed at analyzing
functional variability of communities based on intraspecific trait
variation. 2. Functional abundance of species in a given community was
estimated for two models of proportional and nonproportional random
sampling of individuals of each species for determining trait profiles
of the selected individuals. The intraspecific trait variabilities
obtained for each separate species were incorporated together with
taxonomic abundance of those species to assess species functional
abundance. 3. Two examples demonstrate the pipeline of calculations of
the functional abundance for the two corresponding models. Possible
applications of the functional abundance and related technical issues
are briefly discussed.