In the Three Domain taxonomy of life, Genus is the seventh of the eight ranks:

  1. Domain
  2. Kingdom
  3. Phylum
  4. Class
  5. Order
  6. Family
  7. Genus
  8. Species

For Homo Sapiens (us), the genus is Homo:


The genus of a surface is a topological invariant that is (roughly) the number of holes in the surface, usually denoted as g. For example, the genus of a coffee cup or a torus is 1, whilst the genus of a sphere is 0.

It is related to the Euler characteristic by the formula χ = 2 - 2g.

Strictly speaking, the genus is the number of non-intersecting closed curves that can be embedded in a surface without dividing it up.

Ge"nus (?), n.; pl. Genera (#). [L., birth, race, kind, sort; akin to Gr. . See Gender, and cf. Benign.]

1. Logic

A class of objects divided into several subordinate species; a class more extensive than a species; a precisely defined and exactly divided class; one of the five predicable conceptions, or sorts of terms.

2. Biol.

An assemblage of species, having so many fundamental points of structure in common, that in the judgment of competent scientists, they may receive a common substantive name. A genus is not necessarily the lowest definable group of species, for it may often be divided into several subgenera. In proportion as its definition is exact, it is natural genus; if its definition can not be made clear, it is more or less an artificial genus.

⇒ Thus in the animal kingdom the lion, leopard, tiger, cat, and panther are species of the Cat kind or genus, while in the vegetable kingdom all the species of oak form a single genus. Some genera are represented by a multitude of species, as Solanum (Nightshade) and Carex (Sedge), others by few, and some by only one known species.

Subaltern genus Logic, a genus which may be a species of a higher genus, as the genus denoted by quadruped, which is also a species of mammal. -- Summum genus [L.] Logic, the highest genus; a genus which can not be classed as a species, as being .


© Webster 1913.

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