Binomen

In zoological nomenclature, a binomen (plural: binomina), also known as a binominal name, is the two-part name of a species. The term was introduced in 1953, abolishing the previously used "binomial name" (as being inaccurate). A binomen consists of a generic name (for the genus) and a specific name (for the species).

Often, although it is not a requirement, the binomen is typeset in italics, thus Canis lupus is the usual form (but Canis lupus or even Canis lupus are allowed). The first letter of the name (which also is the first letter of the generic name) is capitalised, and the first letter of the specific name must be lower-case. If the generic name has already been mentioned in the same paragraph, it is often abbreviated to the initial letter in subsequent uses of the binomen, for example, C. lupus.

In a taxonomic publication, the first mention of a binomen, or of any zoological name, is often accompanied by the name of the author, often supplemented by the date, and sometimes publication details. This not only indicates who published the name, and the date of the publication, but is essential to determine priority.

Binomina are part of binominal nomenclature, the system of scientific nomenclature in which a species, but only a species, gets a name that is a combination of two names. Binomina may be said to be a particular form of binomials. Zoological nomenclature is governed by the International Code of Zoological Nomenclature. Other codes of nomenclature, which use other forms of binomial nomenclature, apply to other types of organisms.

A trinomen is the three-part name of a subspecies.