Genus

In biological classification, a genus (plural: genera) sits between the ranks of species and family, grouping together closely related living or fossil organisms, including viruses. Under binomial nomenclature, the genus name is the first part of every species’ two-part scientific name. Taxonomists decide what belongs in a genus, but because the rules for defining one aren’t strictly set, different experts often end up with different classifications. Still, a newly defined genus is generally expected to meet three criteria: it should be monophyletic (including all descendants of a common ancestor), reasonably compact (not unnecessarily large), and distinct in evolutionarily meaningful ways—such as ecology, morphology, or biogeography—since DNA sequences reflect divergence rather than cause it, except where they directly block gene flow. Genera should also be made up of phylogenetic units comparable to those in other genera.

The word “genus” comes from Latin, related to *gignere* (“to bear” or “to give birth to”). French botanist Joseph Pitton de Tournefort is credited with founding the modern concept of genera, and Swedish taxonomist Carl Linnaeus popularized its use in his 1753 work *Species Plantarum*.

In scientific writing, the genus name—also called the generic name—is always capitalized. It’s a key part of binomial nomenclature, where it’s paired with the species name to give each organism a unique, Latinized scientific name. This contrasts with common names, which vary by language and region. For example, the gray wolf is *Canis lupus*: *Canis* (Latin for “dog”) is the genus, and *lupus* (“wolf”) is the species. A botanical example is *Hibiscus arnottianus*, a Hawaiian hibiscus. The species name is written in lowercase and can be followed by subspecies (in zoology) or infraspecific names (in botany). When the genus is clear from context, it may be shortened to its initial letter, like *C. lupus*. The genus name (or its abbreviation) always leads the scientific name, even for subspecies, such as *Canis lupus lupus* or *Hibiscus arnottianus* subsp. *immaculatus*. By convention, these Latinized names are italicized.

For all groups except viruses, genus names can include their authorities—typically “author, year” in zoology (e.g., *Canis* Linnaeus, 1758) or a standard abbreviated author name in botany (e.g., *Hibiscus* L.).

Each genus should have a des