Binomial Nomenclature

Binomial nomenclature (also called binominal nomenclature or binary nomenclature) is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just "binomial"), a binomen or a scientific name; more informally it is also called a Latin name. The first part of the name identifies the genus to which the species belongs; the second part identifies the species within the genus. For example, humans belong to the genus Homo and within this genus to the species Homo sapiens. The formal introduction of this system of naming species is credited to Swedish natural scientist Carl Linnaeus, effectively beginning with his work Species Plantarum in 1753.

The application of binomial nomenclature is now governed by various internationally agreed codes of rules, of which the two most important are the International Code of Zoological Nomenclature (ICZN) for animals and the International Code of Nomenclature for algae, fungi, and plants (ICN) for plants. Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules.

In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not, even when derived from a proper noun such as the name of a person or place. Similarly, both parts are italicized when a binomial name occurs in normal text. Thus the binomial name of the annual phlox (named after botanist Thomas Drummond) is now written as Phlox drummondii.

In scientific works, the "authority" for a binomial name is usually given, at least when it is first mentioned, and the date of publication may be specified.

• In zoology
  • "Patella vulgata Linnaeus, 1758". The name "Linnaeus" tells the reader who it was that first published a description and name for this species of sea snail; 1758 is the date of the publication in which the original description can be found (in this case the 10th edition of the book Systema Naturae).
  • "Passer domesticus (Linnaeus, 1758)". The original name given by Linnaeus was Fringilla domestica, the ICZN does not require the name of the person who changed the genus or the date on which the change was made to be given.
• In botany
  • "Amaranthus retroflexus L." – "L." is the standard abbreviation used in botany for "Linnaeus".
  • "Hyacinthoides italica (L.) Rothm. – Linnaeus first named this bluebell species Scilla italica; Rothmaler transferred it to the genus Hyacinthoides; the ICN does not require that the dates of either publication be specified.