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In
taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
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, name or a scientific name; more informally it is also historically called a Latin name. The first part of the name – the '' generic name'' – identifies the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
to which the species belongs, whereas the second part – the specific name or specific epithet – distinguishes the species within the genus. For example, modern humans belong to the genus ''
Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' ( modern humans), plus several extinct species classified as either ancestral to or closely rela ...
'' and within this genus to the species ''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture ...
''. '' Tyrannosaurus rex'' is likely the most widely known binomial. The ''formal'' introduction of this system of naming species is credited to
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, ...
, effectively beginning with his work ''
Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the ...
'' in 1753. But as early as 1622, Gaspard Bauhin introduced in his book ''Pinax theatri botanici'' (English, ''Illustrated exposition of plants'') containing many names of genera that were later adopted by Linnaeus. 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 The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...
'' (''ICZN'') for animals and the ''
International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...
'' (''ICNafp''). Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in terminology they use and in their particular rules. In modern usage, the first letter of the generic name is always capitalized in writing, while that of the specific epithet is not, even when derived from a proper noun such as the name of a person or place. Similarly, both parts are italicized 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''. Often, after a species name is introduced in a text, the generic name is abbreviated to the first letter in subsequent mentions (e.g., ''P. drummondii''). In scientific works, the
authority In the fields of sociology and political science, authority is the legitimate power of a person or group over other people. In a civil state, ''authority'' is practiced in ways such a judicial branch or an executive branch of government.''T ...
for a binomial name is usually given, at least when it is first mentioned, and the year of publication may be specified. *In
zoology Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, an ...
** "''
Patella vulgata ''Patella vulgata'', common name the common limpet or common European limpet is a species of sea snail. It is a typical true limpet; a marine gastropod mollusc in the family Patellidae, with gills.Gofas, S. (2014). Patella vulgata Linnaeus, 1758 ...
'' Linnaeus, 1758". The name "Linnaeus" tells the reader who published the name and description for this species; 1758 is the year the name and original description was published (in this case, in 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 placed 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 Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...
**"'' Amaranthus retroflexus'' L." – "L." is the standard abbreviation used for "Linnaeus". **"'' Hyacinthoides italica'' (L.) Rothm." – Linnaeus first named this bluebell species ''Scilla italica''; Rothmaler transferred it to the genus ''Hyacinthoides''; the ''ICNafp'' does not require that the dates of either publication be specified.


Origin

The name is composed of two word-forming elements: ''bi-'' (
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
prefix meaning 'two') and ''nomial (literally 'name'). In Medieval Latin, the related word was used to signify one term in a binomial expression in mathematics. The word nomen (plural nomina) means 'name' in Latin.


History

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 Gaspard Bauhin or Caspar Bauhin ( la, Casparus Bauhinus; 17 January 1560 – 5 December 1624), was a Swiss botanist whose ''Pinax theatri botanici'' (1623) described thousands of plants and classified them in a manner that draws comparisons to t ...
(1560–1624), took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words., p. v The adoption by biologists of a system of strictly binomial nomenclature is due to Swedish botanist and physician
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, ...
(1707–1778). It was in Linnaeus's 1753 ''
Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the ...
'' that he began consistently using a one-word trivial name () after a generic name (genus name) in a system of binomial nomenclature. Trivial names had already appeared in his ''
Critica Botanica ''Critica Botanica'' ("Critique of botany", Leiden, July 1737) was written by Swedish botanist, physician, zoologist and naturalist Carl Linnaeus (1707–1778). The book was published in Germany when Linnaeus was 29 with a discursus by the botan ...
'' (1737) and '' Philosophia Botanica'' (1751). This trivial name is what is now known as a
specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bo ...
(''ICNafp'') or specific name (''ICZN''). The Bauhins' genus names were retained in many of these, but the descriptive part was reduced to a single word. 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 ''Tradescantia virginiana'', the Virginia spiderwort, is a species of flowering plant in the family Commelinaceae. It is the type species of '' Tradescantia'' native to the eastern United States. It is commonly grown in many gardens and also foun ...
'', 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 Alexander III of Macedon ( grc, Ἀλέξανδρος, Alexandros; 20/21 July 356 BC – 10/11 June 323 BC), commonly known as Alexander the Great, was a king of the ancient Greek kingdom of Macedon. He succeeded his father Philip II to ...
, whose armies introduced eastern parakeets to Greece. Linnaeus's trivial names were much easier to remember and use than the parallel polynomial names and eventually replaced them.


Value

The value of the binomial nomenclature system derives primarily from its economy, its widespread use, and the uniqueness and stability of names that the Codes of Zoological and
Botanical Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...
,
Bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...
and Viral Nomenclature provide: * 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 In some cultures, a surname, family name, or last name is the portion of one's personal name that indicates one's family, tribe or community. Practices vary by culture. The family name may be placed at either the start of a person's full name, ...
plus
given name A given name (also known as a forename or first name) is the part of a personal name quoted in that identifies a person, potentially with a middle name as well, and differentiates that person from the other members of a group (typically a ...
(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 ''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture ...
'', '' E. coli'', '' Boa constrictor'', '' Tyrannosaurus rex'', and ''
Aloe vera ''Aloe vera'' () is a succulent plant species of the genus '' Aloe''. It is widely distributed, and is considered an invasive species in many world regions. An evergreen perennial, it originates from the Arabian Peninsula, but grows wild in t ...
''. * Uniqueness. Provided that taxonomists agree as to the limits of a species, it can have only one name that is correct under the appropriate nomenclature code, generally the earliest published if two or more names are accidentally assigned to a species. However, establishing that two names actually refer to the same species and then determining which has priority can be difficult, particularly if the species was named by biologists from different countries. Therefore, a species may have more than one regularly used name; all but one of these names are "
synonyms A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are ...
". Furthermore, within zoology or botany, each species name applies to only one species. If a name is used more than once, it is called a
homonym In linguistics, homonyms are words which are homographs (words that share the same spelling, regardless of pronunciation), or homophones ( equivocal words, that share the same pronunciation, regardless of spelling), or both. Using this definitio ...
. * Stability. Although stability is far from absolute, the procedures associated with establishing binomial names, such as the principle of priority, tend to favor stability. For example, when species are transferred between genera (as not uncommonly happens as a result of new knowledge), the second part of the binomial is kept the same (unless it becomes a homonym). Thus there is disagreement among botanists as to whether the genera '' Chionodoxa'' and '' Scilla'' are sufficiently different for them to be kept separate. Those who keep them separate give the plant commonly grown in gardens in Europe the name '' Chionodoxa siehei''; those who do not give it the name ''Scilla siehei''. The ''siehei'' element is constant. Similarly if what were previously thought to be two distinct species are demoted to a lower rank, such as subspecies, the second part of the binomial name is retained as a trinomen (the third part of the new name). Thus the Tenerife robin may be treated as a different species from the European robin, in which case its name is ''Erithacus superbus'', or as only a subspecies, in which case its name is ''Erithacus rubecula superbus''. The ''superbus'' element of the name is constant, as is its authorship and year of publication.


Problems

Binomial nomenclature for species has the effect that when a species is moved from one genus to another, sometimes the specific name or epithet must be changed as well. This may happen because the specific name is already used in the new genus, or to agree in gender with the new genus if the specific epithet is an adjective modifying the genus name. Some biologists have argued for the combination of the genus name and specific epithet into a single unambiguous name, or for the use of uninomials (as used in nomenclature of ranks above species). Because genus names are unique only within a nomenclature code, it is possible for two or more species to share the same genus name and even the same binomial if they occur in different kingdoms. At least 1,258 instances of genus name duplication occur (mainly between zoology and botany).


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 In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are give ...
, 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 Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
includes both nomenclature and classification. Its first stages (sometimes called "
alpha taxonomy In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are give ...
") are concerned with finding, describing and naming species of living or
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
organisms. Binomial nomenclature is thus an important part of taxonomy as it is the system by which species are named. Taxonomists are also concerned with classification, including its principles, procedures and rules.


Derivation of binomial 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 In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...
. Thus, both parts of the binomial name ''Homo sapiens'' are Latin words, meaning "wise" (''sapiens'') "human/man" (''Homo''). *
Classical Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...
. The genus ''
Rhododendron ''Rhododendron'' (; from Ancient Greek ''rhódon'' "rose" and ''déndron'' "tree") is a very large genus of about 1,024 species of woody plants in the heath family (Ericaceae). They can be either evergreen or deciduous. Most species are nati ...
'' was named by Linnaeus from the Greek word , itself derived from ''rhodon'', "rose", and ''dendron'', "tree". Greek words are often converted to a Latinized form. Thus coca (the plant from which cocaine is obtained) has the name '' Erythroxylum coca''. ''Erythroxylum'' is derived from the Greek words ''erythros'', red, and ''xylon'', wood. The Greek neuter ending - (-on) is often converted to the Latin neuter ending -um. * Other languages. The second part of the name '' Erythroxylum coca'' is derived from ''kuka'', the name of the plant in Aymara and Quechua. Since many dinosaur fossils were found in Mongolia, their names often use Mongolian words, e.g. '' Tarchia'' from ''tarkhi'', meaning "brain", or '' Saichania'' meaning "beautiful one". * Names of people (often naturalists or biologists). The name '' Magnolia campbellii'' commemorates two people: Pierre Magnol, a French botanist, and Archibald Campbell, a doctor in
British India The provinces of India, earlier presidencies of British India and still earlier, presidency towns, were the administrative divisions of British governance on the Indian subcontinent. Collectively, they have been called British India. In one ...
. * Names of places. The lone star tick, ''
Amblyomma americanum ''Amblyomma americanum'', also known as the lone star tick, the northeastern water tick, or the turkey tick, or the "Cricker Tick", is a type of tick indigenous to much of the eastern United States and Mexico, that bites painlessly and commonly ...
'', is widespread in the United States. * Other sources. Some binomial names have been constructed from taxonomic anagrams or other re-orderings of existing names. Thus the name of the genus '' Muilla'' is derived by reversing the name '' Allium''. Names may also be derived from
jokes A joke is a display of humour in which words are used within a specific and well-defined narrative structure to make people laugh and is usually not meant to be interpreted literally. It usually takes the form of a story, often with dialogue, ...
or puns. For example, Ratcliffe described a number of species of rhinoceros beetle, including '' Cyclocephala nodanotherwon''. The first part of the name, which identifies the genus, must be a word which can be treated as a Latin
singular Singular may refer to: * Singular, the grammatical number that denotes a unit quantity, as opposed to the plural and other forms * Singular homology * SINGULAR, an open source Computer Algebra System (CAS) * Singular or sounder, a group of boar ...
noun in the
nominative case In grammar, the nominative case ( abbreviated ), subjective case, straight case or upright case is one of the grammatical cases of a noun or other part of speech, which generally marks the subject of a verb or (in Latin and formal variants of Eng ...
. It must be unique within the purview of each nomenclatural code, but can be repeated between them. Thus '' Huia recurvata'' is an extinct species of plant, found as
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s in
Yunnan Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the ...
, China, whereas '' Huia masonii'' is a species of frog found in
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
, Indonesia. 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 Gender is the range of characteristics pertaining to femininity and masculinity and differentiating between them. Depending on the context, this may include sex-based social structures (i.e. gender roles) and gender identity. Most culture ...
. Latin has three genders, masculine, feminine and neuter, shown by varying endings to nouns and adjectives. The
house sparrow The house sparrow (''Passer domesticus'') is a bird of the Old World sparrow, sparrow family Passeridae, found in most parts of the world. It is a small bird that has a typical length of and a mass of . Females and young birds are coloured pale ...
has the binomial name ''Passer domesticus''. Here ''domesticus'' ("domestic") simply means "associated with the house". The sacred bamboo is ''Nandina domestica'' rather than ''Nandina domesticus'', since ''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 In grammar, the genitive case ( abbreviated ) is the grammatical case that marks a word, usually a noun, as modifying another word, also usually a noun—thus indicating an attributive relationship of one noun to the other noun. A genitive can a ...
(possessive) case. The genitive case is constructed in a number of ways in Latin, depending on the
declension In linguistics, declension (verb: ''to decline'') is the changing of the form of a word, generally to express its syntactic function in the sentence, by way of some inflection. Declensions may apply to nouns, pronouns, adjectives, adverbs, and ...
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 '' Magnolia hodgsonii'', or the olive-backed pipit (''Anthus hodgsoni''). The meaning is "of the person named", so that ''Magnolia hodgsonii'' means "Hodgson's magnolia". The ''-ii'' or ''-i'' endings show that in each case Hodgson was a man (not the same one); had Hodgson been a woman, ''hodgsonae'' would have been used. The person commemorated in the binomial name is not usually (if ever) the person who created the name; for example ''Anthus hodgsoni'' was named by Charles Wallace Richmond, in honour of Hodgson. Rather than a person, the noun may be related to a place, as with '' Latimeria chalumnae'', meaning "of the Chalumna River". Another use of genitive nouns is in, for example, the name of the bacterium ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...
'', where ''coli'' means "of the colon". This formation is common in parasites, as in '' Xenos vesparum'', where ''vesparum'' means "of the wasps", since ''Xenos vesparum'' is a parasite of wasps. Whereas the first part of a binomial name must be unique within the purview of each nomenclatural code, 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 each code.


Codes

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 Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms. To an end-user who only deals with names of species, with some awareness that species ...
. The ''
International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...
'' (''ICZN'') governs the naming of animals, the ''
International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...
'' (''ICNafp'') that of plants (including
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, bl ...
), and the '' International Code of Nomenclature of Bacteria'' (''ICNB'') that of
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
(including
Archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaeba ...
).
Virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...
names are governed by the '' International Committee on Taxonomy of Viruses'' (''ICTV''), a taxonomic code, which determines taxa as well as names. These codes differ in certain ways, e.g.: * "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 binomial name is also called a binomen (plural binomina) or name. * 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 (''ICNafp''), 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 codes. * The ''ICNafp'', 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 binomen ''Bison bison''; a name of this kind would not be allowed for a plant. * The starting points, the time from which these codes are in effect (retroactively), vary from group to group. In
botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...
the starting point will often be in 1753 (the year Carl Linnaeus first published ''
Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the ...
''). In
zoology Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, an ...
the starting point is 1758 (1 January 1758 is considered the date of the publication of Linnaeus's ''
Systema Naturae ' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial ...
'', 10th Edition, and also Clerck's ''Aranei Svecici''). Bacteriology started anew, with a starting point on 1 January 1980. Unifying the different codes into a single code, the "''BioCode''", has been suggested, although implementation is not in sight. (There is also a published code for a different system of biotic nomenclature which does not use ranks above species, but instead names
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
s. This is called the '' PhyloCode''.)


Differences in handling personal names

As noted above, there are some differences between the codes in the way in which binomials can be formed; for example the ''ICZN'' allows both parts to be the same, while the ''ICNafp'' does not. Another difference is in the way in which personal names are used in forming specific names or epithets. The ''ICNafp'' sets out precise rules by which a personal name is to be converted to a specific epithet. In particular, names ending in a consonant (but not "er") are treated as first being converted into Latin by adding "-ius" (for a man) or "-ia" (for a woman), and then being made genitive (i.e. meaning "of that person or persons"). This produces specific epithets like ''lecardii'' for Lecard (male), ''wilsoniae'' for Wilson (female), and ''brauniarum'' for the Braun sisters. By contrast the ''ICZN'' does not require the intermediate creation of a Latin form of a personal name, allowing the genitive ending to be added directly to the personal name. This explains the difference between the names of the plant ''Magnolia hodgsonii'' and the bird ''Anthus hodgsoni''. Furthermore, the ''ICNafp'' requires names not published in the form required by the code to be corrected to conform to it, whereas the ''ICZN'' is more protective of the form used by the original author.


Writing binomial names

By tradition, the binomial names of species are usually typeset in italics; for example, ''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture ...
''. Generally, the binomial should be printed in a font style different from that used in the normal text; for example, "''Several more ''Homo sapiens'' fossils were discovered''." When handwritten, a binomial name should be underlined; for example, Homo sapiens. The first part of the binomial, the genus name, is always written with an initial capital letter. 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''. In current usage, the second part is never written with an initial capital. 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 "''Canis lupus'', ''C. aureus'', ''C. simensis''". In rare cases, this abbreviated form has spread to more general use; for example, the bacterium ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...
'' is often referred to as just ''E. coli'', and '' Tyrannosaurus rex'' is perhaps even better known simply as ''T. rex'', these two both often appearing in this form in popular writing even where the full genus name has not already been given. 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: "''Canis'' sp." means "an unspecified species of the genus '' Canis''", while "''Canis'' spp." means "two or more species of the genus ''Canis''". (These abbreviations should not be confused with the abbreviations "ssp." (zoology) or "subsp." (botany), plurals "sspp." or "subspp.", referring to one or more
subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. Not all specie ...
. See trinomen (zoology) and infraspecific name.) 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.


Authority

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 ''ICNafp'' 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 ''ICNafp'' also requires the person who made the change to be given. In the ''ICNafp'', the original name is then called the
basionym In the scientific name of organisms, basionym or basyonym means the original name on which a new name is based; the author citation of the new name should include the authors of the basionym in parentheses. The term "basionym" is used in both bota ...
. Some examples: *(Plant) '' Amaranthus retroflexus'' L. – "L." is the standard abbreviation for "Linnaeus"; the absence of parentheses shows that this is his original name. *(Plant) '' Hyacinthoides italica'' (L.) Rothm. – Linnaeus first named the Italian bluebell ''Scilla italica''; that is the basionym. Rothmaler later transferred it to the genus ''Hyacinthoides''. *(Animal) '' Passer domesticus'' (Linnaeus, 1758) – the original name given by Linnaeus was ''Fringilla domestica''; unlike the ''ICNafp'', the ''ICZN'' does not require the name of the person who changed the genus (
Mathurin Jacques Brisson Mathurin Jacques Brisson (; 30 April 1723 – 23 June 1806) was a French zoologist and natural philosopher. Brisson was born at Fontenay-le-Comte. The earlier part of his life was spent in the pursuit of natural history; his published wo ...
) to be given.


Other ranks

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 ''ICNafp''. 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''.


See also

*
Glossary of scientific naming This is a list of terms and symbols used in scientific names for organisms, and in describing the names. For proper parts of the names themselves, see List of Latin and Greek words commonly used in systematic names. Note that many of the abbrevi ...
*
Botanical name A botanical name is a formal scientific name conforming to the ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) and, if it concerns a plant cultigen, the additional cultivar or Group epithets must conform to the ''Interna ...
* Hybrid name (botany) * List of botanists by author abbreviation *
List of Latin and Greek words commonly used in systematic names This list of Latin and Greek words commonly used in systematic names is intended to help those unfamiliar with classical languages to understand and remember the scientific names of organisms. The binomial nomenclature used for animals and plants i ...
* List of organisms named after famous people * List of zoologists by author abbreviation * Scientific terminology *
Species description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have ...
*
Undescribed taxon In taxonomy, an undescribed taxon is a taxon (for example, a species) that has been discovered, but not yet formally described and named. The various Nomenclature Codes specify the requirements for a new taxon to be validly described and named. ...


Notes


References


Bibliography

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Further reading

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External links


Curiosities of Biological Nomenclature

NCBI Taxonomy Database
{{authority control *