Genus

A genus (/ˈdʒiːnəs/, pl. genera /ˈdʒɛnərə/) is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus. A genus (/ˈdʒiːnəs/, pl. genera /ˈdʒɛnərə/) is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus. The composition of a genus is determined by a taxonomist. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera. The term 'genus' comes from the Latin genus ('origin, type, group, race'), a noun form cognate with gignere ('to bear; to give birth to'). Linnaeus popularized its use in his 1753 Species Plantarum, but the French botanist Joseph Pitton de Tournefort (1656–1708) is considered 'the founder of the modern concept of genera'. The scientific name (or the scientific epithet) of a genus is also called the generic name; it is always capitalised. It plays a fundamental role in binomial nomenclature, the system of naming organisms, where it is combined with the scientific name of a species: see Specific name (botany) and Specific name (zoology). The rules for the scientific names of organisms are laid down in the Nomenclature Codes, which allow each species a single unique name that, for 'animals' (including protists), 'plants' (also including algae and fungi) and prokaryotes (Bacteria and Archaea), is Latin and binomial in form; this contrasts with common or vernacular names, which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses, the standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf's scientific name is Canis lupus, with Canis (Lat. 'dog') being the generic name shared by the wolf's close relatives and lupus (Lat. 'wolf') being the specific name particular to the wolf. A botanical example would be Hibiscus arnottianus, a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany. When the generic name is already known from context, it may be shortened to its initial letter, for example C. lupus in place of Canis lupus. Where species are further subdivided, the generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example Canis lupus familiaris for the domestic dog (when considered a subspecies of the gray wolf) in zoology, or as a botanical example, Hibiscus arnottianus ssp. immaculatus. Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics.