Subspecies

In biological classification, subspecies (commonly abbreviated subsp. or ssp.) is
 * a taxonomic rank subordinate to species, or
 * a taxonomic unit, a taxon in that rank (plural: subspecies). A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one.

The differences between subspecies are usually less distinct than the differences between species. The characteristics attributed to subspecies generally have evolved as a result of geographical distribution or isolation.