noun, singular or plural: species
(1) The lowest taxonomic rank, and the most basic unit or category of biological classification.
(2) An individual belonging to a group of organisms (or the entire group itself) having common characteristics and (usually) are capable of mating with one another to produce fertile offspring. Failing that (for example the Liger) It has to be ecologically and recognisably the same.
A species is given a two-part name: the generic name and the specific name (or specific epithet). For example, Allium cepa (commonly known as onion)