Taxa count Count of unique taxa. A taxon (plural: taxa) is a group of one (or more) populations of organism(s), which is judged to be a unit. Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV. ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables.