In zoological nomenclature, a binomen, or binominal name, is the name of a species. The term was introduced in 1953, abolishing the previously used "binomial name" (as being inaccurate).
A binomen is a name consisting of two names: a generic name and a specific name. Both names are typeset in italics, but only the generic name is capitalised.
- Tyrannosaurus rex the tyrant-lizard king.
If the generic name has already been mentioned in the same paragraph, it is often abbreviated to the initial letter in subsequent uses (T. rex).
In a taxonomic publication, the binomen, when first mentioned, is often accompanied by the name of the author and 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.
A binomen is part of binominal nomenclature, which holds only for animals. For other organisms other Codes of Nomenclature may apply, which use binomial nomenclature (not to be confused with the mathematical "binomial"). In a broad sense, a binomen may be said to be a particular form of a binomial.