Genus

A genus (plural: genera) is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain, kingdom, phylum, class, order, family, genus, and species. The term comes from Latin genus "descent, family, type, gender" (plurals: genera), cognate with - genos, "race, stock, kin".

Types and genera
Because of the rules of scientific naming, or "binomial nomenclature", each genus must have a designated type species (see Type (zoology) ) which defines the genus; the generic name is permanently associated with the type specimen of its type species. Should this specimen turn out to be assignable to another genus, the genus name linked to it becomes a junior synonym, and the remaining taxa in the now-invalid genus need to be reassessed. See scientific classification and Nomenclature Codes for more details of this system. Also see type genus.