genus

Genus is a rank in biological classification that groups together species that are closely related and share a recent common ancestor. It sits above species and below family. A genus comprises one or more species; the members of a genus are typically more similar to each other than to species in other genera. In binomial nomenclature, the scientific name of a species is formed by combining its genus name with a specific epithet, as in Homo sapiens or Canis lupus. The genus name is always capitalized and, in standard scientific writing, the full species name is italicized.

Examples of well-known genera include Homo (humans and close relatives), Canis (dogs, wolves, and related animals), and Felis (domestic cats). Some genera are monotypic, containing a single species, such as Ginkgo (Ginkgo biloba) in modern classifications. Other genera are large and contain many species.

Taxonomy and systematics: Circumscription of a genus can change as new evidence from morphology, genetics, and phylogenetic analyses becomes available. Genera are organized into families, which in turn are grouped into higher ranks such as orders and classes. Conversely, species can be reassigned to different genera when new relationships are recognized.

Usage and limitations: The genus is a conventional unit that helps organize biodiversity, but its designation reflects current hypotheses about evolutionary relationships. Taxonomic boundaries can be revised as scientific understanding progresses, and different taxonomic treatments may exist across groups of organisms.