Subspecies - geographically localized populations that are genetically and taxonomically (at least 75% of the distinguishable individuals) different from other populations of the same species.

The basic systematic unit is the species. A species is a set of individuals inhabiting a certain area), characterized by morphological similarity, freely interbreeding and genetically homogeneous. Within a species, subspecies are sometimes distinguished. These are, as a rule, geographically isolated groups of individuals of the same species that have morphological and biological differences and do not interbreed due to the discontinuity of the range.

A subspecies is a structural unit of a species. A species usually consists of one or more subspecies, which are sometimes called geographic races. Subspecies are distinguished from each other by morphological features, lifestyle, and inhabitation of a certain geographical area. There cannot be two subspecies in one body of water - a river or a lake.

The name of a subspecies includes three words. To the name of the species to which the subspecies belongs and consisting of the first two words is added a third word, meaning the subspecies itself, e.g. Salmo trutta truita Linnaeus - or Coregonus lavaretus pidschian (Gmelin) - murrelet or Siberian whitefish, which is a subspecies of the common whitefish - Coregonus lavaretus.