genus

1. Biology any of the taxonomic groups into which a family is divided and which contains one or more species. For example, Vulpes (foxes) is a genus of the dog family (Canidae)

2. Logic a class of objects or individuals that can be divided into two or more groups or species

3. Maths a number characterizing a closed surface in topology equal to the number of handles added to a sphere to form the surface. A sphere has genus 0, a torus, genus 1, etc.

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

genus

[′jē·nəs]

(mathematics)

An integer associated to a surface which measures the number of holes in the surface.

(systematics)

A taxonomic category that includes groups of closely related species; the principal subdivision of a family.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Genus

a major taxonomic category that phylogenetically unites closely related species. For example, various cat species (European wildcat, jungle cat, leopard cat) are united in the genus Felis. Various pine species (Scotch pine, Siberian pine) form the genus Pinus. The scientific name of a genus is designated by a single Latin word.

Genera may consist of many species. For example, some insect and plant genera contain hundreds or thousands of species. Some genera comprise only one or a few species.

Genera having only one species, such as Desmana or Welwitschia, are called monotypic. Genera with several species are often divided into subgenera, which unite especially closely related species. Each genus belongs to a family, but between these two taxonomic categories there are often intermediate ones. For example, tribes are grouped in subfamilies, which in turn are grouped in families.

In paleobotany there also are organ genera and formal genera.

V. G. GEPTNER and M. E. KIRPICHNIKOV