Binomial nomenclature
In
biology,
binomial nomenclature is the formal method of naming
species. As the word "binomial" suggests, the scientific name of a species is formed by the combination of two terms: the
genus name and the species descriptor. Although the fine detail will differ, there are certain aspects which are universally adopted:
* Scientific names are usually printed in italics, such as
Homo sapiens. When handwritten they should be
underlined.
* The first term (genus name / generic name) is
always capitalized, while the specific descriptor (in
zoology, the "
specific name", in
botany, the "
specific epithet") will not be, even when derived from a proper name. For example,
Canis lupus or
Anthus hodgsoni. (But note that this is a modern convention:
Carolus Linnaeus always capitalized the specific descriptor, and up to the early
20th century it was common to capitalize the specific descriptor if it was based on a proper name.)
* In scholarly texts, the main entry for the binomial is followed by the abbreviated name of the scientist who first published the classification. For example:
Amaranthus retroflexus L. This keeps the binomial unique even when later scientists need to reclassify species or further distinguish between species.
* When used with a common name, the scientific name usually follows in parentheses, for example, "the house sparrow (
Passer domesticus) is endangered."
* The scientific name should generally be written in full when it is first used or when several species from the same genus are being listed or discussed in the same paper or report. It may then be abbreviated by just using an initial (and period) for the genus; for example
Canis lupus becomes
C. lupus. In rare cases this abbreviation form has spread to more general use — for example the bacterium
Escherichia coli is often referred to as just
E. coli, and
Tyrannosaurus rex is perhaps even better known simply as
T. rex.
* The abbreviation "sp." (or "spec.") is used when the actual specific name is not known: for example
Canis sp. denotes "a species of the genus
Canis". The abbreviation "spp." (plural) indicates "several unknown species".
* The abbreviation "
cf." is used when the identification is not confirmed: for example
Corvus cf. splendens indicates that the species is in doubt.
* Binomial nomenclature is also referred to as the 'Binomial Classification System'.
The adoption of a system of binomial nomenclature is due to
Swedish botanist and
physician Carolus Linnaeus (1707–1778) who attempted to describe the entire known natural world and gave every species (
mineral,
vegetable or
animal) a two-part name. However, binomial nomenclature in various forms existed before Linnaeus, and was used by the
Bauhins, who lived nearly two hundred years before Linnaeus. Before Linnaeus hardly anybody used binomial nomenclature. After Linnaeus, almost everybody did.
The value of the binomial nomenclature
system derives primarily from its economy, its widespread use, and the stability of names it generally favors:
* Every species can be unambiguously identified with just two words.
* The same name can be used all over the world, in all languages, avoiding difficulties of translation.
* Although such stability as exists is far from absolute, the procedures associated with establishing binomial nomenclature tend to favor stability. For example, when species are transferred between genera (as not uncommonly happens as a result of new knowledge), if possible the species descriptor is kept the same. Similarly if what were previously thought to be distinct species are demoted from species to a lower rank, former species names may be retained as infraspecific descriptors.
Despite the rules favoring stability and uniqueness, in practice a single species may have several scientific names in circulation, depending largely on taxonomic point of view (see
synonymy).
A major source of instability is the resurrection of forgotten names, which can claim priority of publication. In this case, however,
conservation according to the
nomenclature Codes is possible.
From the mid nineteenth century onwards it became ever more apparent that a body of rules was necessary to govern scientific names. In the course of time these became
Nomenclature Codes governing the naming of animals (
ICZN),
plants (incl.
Fungi,
cyanobacteria) (
ICBN),
bacteria (
ICNB) and
viruses. These Codes differ.
* For example, the
ICBN, the plant
Code does not allow
tautonyms, whereas the
ICZN, the animal
Code does allow
tautonymy.
* The starting points, the time from which these
Codes are in effect (retroactively), vary from group to group. In
botany the starting point will often be in 1753, in
zoology in 1758.
Bacteriology started anew, with a starting point in 1980).
A
BioCode has been suggested to replace several codes, although implementation is not in sight. There also is debate concerning development of a
PhyloCode to name
clades of
phylogenetic trees, rather than taxa. Proponents of the
PhyloCode use the name "Linnaean Codes" for the joint existing
Codes and "Linnaean taxonomy" for the scientific classification that uses these existing
Codes.
The genus name and species descriptor may come from any source whatsoever. Often they are
Latin words, but they may also come from
Ancient Greek, from a place, from a person (preferably a naturalist), a name from a local language, etc. In fact, taxonomists come up with specific descriptors from a variety of sources, including inside-jokes and puns.
However, names are always treated grammatically as if they were a
Latin sentence. For this reason the name of a species is sometimes called its "Latin name," although this terminology is frowned upon by
biologists (and
philologists), who prefer the phrase
scientific name.
There is a separate
list of Latin and Greek words commonly used in systematic names.
The
genus name must be unique inside each kingdom.
Species names are commonly reused, and are usually an adjectival modifier to the genus name, which is a noun.
Family names are often derived from a common genus within the family.
*
Trinomial nomenclature*
Hybrid name*
Curiosities of Biological Nomenclature*
The Language of Horticulture*
Principles of Nomenclature of Zoological Taxa
