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, BINOMINAL NAME 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 – the SPECIFIC NAME or SPECIFIC EPITHET –
identifies the species within the genus. For example, humans belong to
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). 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 (or underlined in handwriting). 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 limpet; 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 parentheses indicate that the species is now considered to belong in a different genus. The ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, although nomenclatorial catalogs usually include such information.
* In botany
Amaranthus retroflexus L." – "L." is the standard abbreviation
used in botany for "Linnaeus".
Hyacinthoides italica (L.) Rothm. – Linnaeus first named this
* 1 Origin * 2 History * 3 Value * 4 Problems * 5 Relationship to classification and taxonomy * 6 Derivation of binomial names * 7 Codes
* 8 Writing binomial names
* 8.1 Authority
* 9 Other ranks * 10 See also * 11 Notes * 12 References * 13 Bibliography * 14 External links
The name is composed of two word-forming elements: "bi", a Latin prefix for two, and "nomial", which is a noun commonly used in mathematics to define a name or term.
See also: Biological classification: Early systems Carl Linnaeus (1707–1778), a Swedish botanist, invented the modern system of binomial nomenclature
Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name that was from one to several words long. Together they formed a system of polynomial nomenclature. These names had two separate functions. First, to designate or label the species, and second, to be a diagnosis or description; however these two goals were eventually found to be incompatible. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; but as more species were discovered the names necessarily became longer and unwieldy, for instance Plantago foliis ovato-lanceolatus pubescentibus, spica cylindrica, scapo tereti ("Plantain with pubescent ovate-lanceolate leaves, a cylindric spike and a terete scape"), which we know today as Plantago media .
Such "polynomial names" may sometimes look like binomials, but are significantly different. For example, Gerard's herbal (as amended by Johnson) describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort; the second, Phalangium non ramosum, Unbranched Spiderwort. The other ... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels.
The Bauhins , in particular Caspar
Bauhin (1560–1624), took some
important steps towards the binomial system, by pruning the Latin
descriptions, in many cases to two words. The adoption by biologists
of a system of strictly binomial nomenclature is due to Swedish
botanist and physician Carl von Linné, more commonly known by his
Linnaeus's trivial names introduced an important new idea, namely that the function of a name could simply be to give a species a unique label. This meant that the name no longer need be descriptive; for example both parts could be derived from the names of people. Thus Gerard's phalangium ephemerum virginianum became Tradescantia virginiana , where the genus name honoured John Tradescant the younger , an English botanist and gardener. A bird in the parrot family was named Psittacus alexandri , meaning "Alexander's parrot", after Alexander the Great whose armies introduced eastern parakeets to Greece. Linnaeus' trivial names were much easier to remember and use than the parallel polynomial names and eventually replaced them.
The value of the binomial nomenclature system derives primarily from its economy, its widespread use, and the uniqueness and stability of names it generally favors:
* Economy. Compared to the polynomial system which it replaced, a
binomial name is shorter and easier to remember. It corresponds to
the widespread system of family name plus given name (s) used to name
people in many cultures.
* Widespread use. The binomial system of nomenclature is governed by
international codes and is used by biologists worldwide. A few
binomials have also entered common speech, such as
Because binomials are unique only within a kingdom, it is possible for two or more species to share the same binomial if they occur in different kingdoms. At least five instances of such binomial duplication occur.
RELATIONSHIP TO CLASSIFICATION AND TAXONOMY
Nomenclature (including binomial nomenclature) is not the same as classification, although the two are related. Classification is the ordering of items into groups based on similarities or differences; in biological classification , species are one of the kinds of item to be classified. In principle, the names given to species could be completely independent of their classification. This is not the case for binomial names, since the first part of a binomial is the name of the genus into which the species is placed. Above the rank of genus, binomial nomenclature and classification are partly independent; for example, a species retains its binomial name if it is moved from one family to another or from one order to another, unless it better fits a different genus in the same or different family, or it is split from its old genus and placed in a newly created genus. The independence is only partial since the names of families and other higher taxa are usually based on genera.
Taxonomy includes both nomenclature and classification. Its first
stages (sometimes called "alpha taxonomy ") are concerned with
finding, describing and naming species of living or fossil organisms.
DERIVATION OF BINOMIAL NAMES
See also: List of Latin and Greek words commonly used in systematic names
A complete binomial name is always treated grammatically as if it were a phrase in the Latin language (hence the common use of the term " Latin name" for a binomial name). However, the two parts of a binomial name can each be derived from a number of sources, of which Latin is only one. These include:
* Latin, either classical or medieval . Thus, both parts of the
The first part of the name, which identifies the genus, must be a
word which can be treated as a
Latin singular noun in the nominative
case . It must be unique within each kingdom , but can be repeated
between kingdoms. Thus Huia recurvata is an extinct species of plant,
found as fossils in
The second part of the name, which identifies the species within the genus, is also treated grammatically as a Latin word. It can have one of a number of forms.
* The second part of a binomial may be an adjective. The adjective
must agree with the genus name in gender .
Latin has three genders,
masculine, feminine and neuter, shown by varying endings to nouns and
adjectives. The house sparrow has the binomial name Passer domesticus.
Here domesticus ("domestic") simply means "associated with the house".
The sacred bamboo is
Nandina domestica rather than Nandina
Nandina is feminine whereas Passer is masculine. The
tropical fruit langsat is a product of the plant Lansium parasiticum,
since Lansium is neuter. Some common endings for
Latin adjectives in
the three genders (masculine, feminine, neuter) are -us, -a, -um (as
in the previous example of domesticus); -is, -is, -e (e.g. tristis,
meaning "sad"); and -or, -or, -us (e.g. minor, meaning "smaller"). For
further information, see
Latin declension: Adjectives .
* The second part of a binomial may be a noun in the nominative
case. An example is the binomial name of the lion, which is Panthera
leo. Grammatically the noun is said to be in apposition to the genus
name and the two nouns do not have to agree in gender; in this case,
Panthera is feminine and leo is masculine.
* The second part of a binomial may be a noun in the genitive
(possessive) case. The genitive case is constructed in a number of
ways in Latin, depending on the declension of the noun. Common endings
for masculine and neuter nouns are -ii or -i in the singular and -orum
in the plural, and for feminine nouns -ae in the singular and -arum in
the plural. The noun may be part of a person's name, often the
surname, as in the
Tibetan antelope Pantholops hodgsonii, the shrub
Whereas the first part of a binomial name must be unique within a kingdom, the second part is quite commonly used in two or more genera (as is shown by examples of hodgsonii above). The full binomial name must be unique within a kingdom.
From the early 19th 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 . The International
Code of Zoological Nomenclature (ICZN) governs the naming of animals,
the International Code of Nomenclature for algae, fungi, and plants
(ICN) that of plants (including cyanobacteria ), and the International
Code of Nomenclature of
* "Binomial nomenclature" is the correct term for botany, although
it is also used by zoologists. Since 1953, "binominal nomenclature"
is the technically correct term in zoology. A binominal name is also
called a binomen (plural binomina).
* Both codes consider the first part of the two-part name for a
species to be the "generic name". In the zoological code (ICZN), the
second part of the name is a "specific name". In the botanical code
(ICN), it is a "specific epithet". Together, these two parts are
referred to as a "species name" or "binomen" in the zoological code;
or "species name", "binomial", or "binary combination" in the
botanical code. "
Species name" is the only term common to the two
* The ICN, the plant Code, does not allow the two parts of a
binomial name to be the same (such a name is called a tautonym ),
whereas the ICZN, the animal Code, does. Thus the American bison has
the binomial Bison bison; a name of this kind would not be allowed for
* 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 (the year
Summary of terminology for the names of species in the ICZN and ICN CODE FULL NAME FIRST PART SECOND PART
ICZN species name, binomen, binominal name generic name, genus name specific name
ICN species name, binary combination, binomial (name) generic name specific epithet
Unifying the different codes into a single code, the " BioCode ", has been suggested, although implementation is not in sight. (There is also a code in development for a different system of classification which does not use ranks, but instead names clades . This is called the PhyloCode .)
WRITING BINOMIAL NAMES
By tradition, the binomial names of species are usually typeset in
italics; for example,
The first part of the binomial, the genus name, is always written with an initial capital letter. In current usage, the second part is never written with an initial capital. Older sources, particularly botanical works published before the 1950s, use a different convention. If the second part of the name is derived from a proper noun, e.g. the name of a person or place, a capital letter was used. Thus the modern form Berberis darwinii was written as Berberis Darwinii. A capital was also used when the name is formed by two nouns in apposition, e.g. Panthera Leo or Centaurea Cyanus.
When used with a common name, the scientific name often follows in parentheses, although this varies with publication. For example, "The house sparrow (Passer domesticus) is decreasing in Europe."
The binomial name should generally be written in full. The exception
to this is when several species from the same genus are being listed
or discussed in the same paper or report, or the same species is
mentioned repeatedly; in which case the genus is written in full when
it is first used, but may then be abbreviated to an initial (and a
period/full stop). For example, a list of members of the genus Canis
might be written as "
The abbreviation "sp." is used when the actual specific name cannot
or need not be specified. The abbreviation "spp." (plural) indicates
"several species". These abbreviations are not italicised (or
underlined). For example: "
The abbreviation "cf. " (i.e. confer in Latin) is used to compare individuals/taxa with known/described species. Conventions for use of the "cf." qualifier vary. In paleontology, it is typically used when the identification is not confirmed. For example, "Corvus cf. nasicus" was used to indicate "a fossil bird similar to the Cuban crow but not certainly identified as this species". In molecular systematics papers, "cf." may be used to indicate one or more undescribed species assumed related to a described species. For example, in a paper describing the phylogeny of small benthic freshwater fish called darters, five undescribed putative species (Ozark, Sheltowee, Wildcat, Ihiyo, and Mamequit darters), notable for brightly colored nuptial males with distinctive color patterns, were referred to as "Etheostoma cf. spectabile" because they had been viewed as related to, but distinct from, Etheostoma spectabile (orangethroat darter). This view was supported in varying degrees by DNA analysis. The somewhat informal use of taxa names with qualifying abbreviations is referred to as open nomenclature and it is not subject to strict usage codes.
In some contexts the dagger symbol ("†") may be used before or after the binomial name to indicate that the species is extinct.
Main articles: Author citation (zoology) and Author citation (botany)
In scholarly texts, at least the first or main use of the binomial name is usually followed by the "authority" – a way of designating the scientist(s) who first published the name. The authority is written in slightly different ways in zoology and botany. For names governed by the ICZN the surname is usually written in full together with the date (normally only the year) of publication. The ICZN recommends that the "original author and date of a name should be cited at least once in each work dealing with the taxon denoted by that name." For names governed by the ICN the name is generally reduced to a standard abbreviation and the date omitted. The International Plant Names Index maintains an approved list of botanical author abbreviations. Historically, abbreviations were used in zoology too.
When the original name is changed, e.g. the species is moved to a different genus, both Codes use parentheses around the original authority; the ICN also requires the person who made the change to be given. Some examples:
Amaranthus retroflexus L. – "L." is the standard
abbreviation for "Linnaeus"; the absence of parentheses shows that
this is his original name.
Hyacinthoides italica (L.) Rothm. – Linnaeus first named
the Italian bluebell
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Binomial nomenclature, as described here, is a system for naming species. Implicitly it includes a system for naming genera, since the first part of the name of the species is a genus name. In a classification system based on ranks there are also ways of naming ranks above the level of genus and below the level of species. Ranks above genus (e.g., family, order, class) receive one-part names, which are conventionally not written in italics. Thus the house sparrow, Passer domesticus, belongs to the family Passeridae . Family names are normally based on genus names, although the endings used differ between zoology and botany.
Ranks below species receive three-part names, conventionally written in italics like the names of species. There are significant differences between the ICZN and the ICN. In zoology, the only rank below species is subspecies and the name is written simply as three parts (a trinomen). Thus one of the subspecies of the olive-backed pipit is Anthus hodgsoni berezowskii. In botany, there are many ranks below species and although the name itself is written in three parts, a "connecting term" (not part of the name) is needed to show the rank. Thus the American black elder is Sambucus nigra subsp. canadensis; the white-flowered form of the ivy-leaved cyclamen is Cyclamen hederifolium f. albiflorum.
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