Species

A species is a group of living beings that can reproduce among themselves (interfertility) and produce fertile descendants.

Species are the fundamental units of classification, which groups living beings together by common morphological, anatomical, physiological, biochemical and genetic characteristics.

Species are grouped into genera and divided into subgroups called varieties, races, strains or populations.
Systematics is the discipline concerned with the inventory of species and their biodiversity and taxonomy provides species with their nomenclature.