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In
taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
, 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 biological classification, 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 individu ...

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, name or a scientific name; more informally it is also called a Latin name. The first part of the name – the '' generic name'' – identifies the
genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure ...
to which the species belongs, while the second part – the specific name or specific epithet – identifies the species within the genus. For example, modern humans belong to the genus ''
Homo ''Homo'' () is the genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, virus ...

Homo
'' and within this genus to the species ''
Homo sapiens Humans (''Homo sapiens'') are the most abundant and widespread of , characterized by and large, complex brains. This has enabled the development of advanced , , and . Humans are highly social and tend to live in complex s composed of many ...

Homo sapiens
''. ''
Tyrannosaurus rex ''Tyrannosaurus'' is a genus of large theropoda, theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosaur ...

Tyrannosaurus rex
'' is probably 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 as Carl von Linné, p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised , the modern system of naming organisms. He is known as the ...

Carl Linnaeus
, effectively beginning with his work ''
Species Plantarum ' (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, i ...
'' in 1753. But as early as 1622,
Gaspard Bauhin Gaspard Bauhin or Caspar Bauhin ( la, Casparus Bauhinus; 17 January 1560 – 5 December 1624), was a Swiss Swiss may refer to: * the adjectival form of Switzerland *Swiss people Places *Swiss, Missouri *Swiss, North Carolina *Swiss, West Virgini ...

Gaspard Bauhin
introduced in his book ''Pinax theatri botanici'' (English, ''Illustrated exposition of plants'') 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 Convention may refer to: * Convention (norm), a custom or tradition, a standard of presentation or conduct ** Treaty, an agreement in international law * Co ...
'' (''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 name A botanical name is a formal scientific name Science (from the Latin Latin (, ...
'' (''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 A proper noun is a noun A noun (from Latin ''nōmen'', literally ''name'') is a word that functions as the name of a specific object or set of objects, such as living creatures, places, actions, qualities, states of existence, or ideas.Exampl ...
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 Captain Thomas Drummond (10 October 1797 – 15 April 1840), from Edinburgh Edinburgh (; sco, Edinburgh; gd, Dùn Èideann ) is the capital city of Scotland and one of its 32 Council areas of Scotland, council areas. Historically part of ...
) is now written as ''
Phlox drummondii ''Phlox drummondii'' (commonly annual phlox or Drummond's phlox) is a flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orde ...

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 Sociology is the study of society, human social behaviour, patterns of social relationships, social interaction, and culture that surrounds everyday life. It is a social science that uses various methods of Empiric ...

authority
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 Biology is the natural science that studies life and living organisms, including their anatomy, physical stru ...
** "''
Patella vulgata ''Patella vulgata'', common name the common limpet or common European limpet is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodive ...

Patella vulgata
'' Linnaeus, 1758". The name "Linnaeus" tells the reader who published the name and description for this species of limpet; 1758 is the year the name and original description was published (in this case, in the 10th edition of the book ''
Systema Naturae ' (originally in Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Rom ...
''). **"''
Passer domesticus The house sparrow (''Passer domesticus'') and also known as the common bird or the common sparrow is a bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless ...

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 wo ...

botany
**"''
Amaranthus retroflexus ''Amaranthus retroflexus'' is a species of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family (biology), f ...
'' L." – "L." is the standard abbreviation used for "Linnaeus". **"''
Hyacinthoides italica ''Hyacinthoides italica'', the Italian bluebell or Italian squill, is a spring-flowering bulbous perennial plant belonging to the family Asparagaceae Asparagaceae is a Family (biology), family of flowering plants, placed in the Order (biology) ...

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: (
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became the dominant la ...

Latin
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 (botany), 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 Gaspard Bauhin, Caspar Bauhin (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 Sweden, Swedish botanist and physician
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his as Carl von Linné, p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised , the modern system of naming organisms. He is known as the ...

Carl Linnaeus
(1707–1778). It was in Linnaeus's 1753 ''
Species Plantarum ' (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, i ...
'' 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'' (1737) and ''Philosophia Botanica'' (1751). This trivial name is what is now known as a specific epithet (botany), specific epithet (''ICNafp'') or specific name (zoology), 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'', where the genus name honoured John Tradescant the Younger, an English botanist and gardener. A bird in the Psittacidae, parrot family was named ''red-breasted parakeet, Psittacus alexandri'', meaning "Alexander's parrot", after Alexander the Great, 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 nomenclature, Zoological and Botanical nomenclature, Botanical, Bacterial nomenclature, Bacterial and Virus nomenclature, 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 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 ''Homo sapiens'', ''E. coli'', ''Boa constrictor'', and ''Tyrannosaurus rex''. * 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 "synonym (taxonomy), synonyms". 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 (biology), homonym. * 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 1240 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 Taxonomy (biology), 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 (biology), 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. 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 Latin, classical or New Latin, medieval. Thus, both parts of the binomial name ''Homo sapiens'' are Latin words, meaning "wise" (''sapiens'') "human/man" (''Homo''). * Ancient Greek, Classical Greek. The genus ''Rhododendron'' was named by Carl Linnaeus, 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 language, Aymara and Quechua languages, Quechua. Since many dinosaur fossils were found in Mongolia, their names often use Mongolian language, 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 Arthur Campbell (doctor), Archibald Campbell, a doctor in British India. * Names of places. The lone star tick, ''Amblyomma americanum'', is widespread in the United States. * Other sources. Some binominal names have been constructed from List of taxa named by anagrams, 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 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 Grammatical number, singular noun in the nominative case. It must be unique within the purview of each nomenclatural code, but can be repeated between them. Thus ''Huia (plant), Huia recurvata'' is an extinct species of plant, found as fossils in Yunnan, China, whereas ''Javan torrent frog, Huia masonii'' is a species of frog found in Java, 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 grammatical gender, 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 Nandina, sacred bamboo is ''Nandina domestica'' rather than ''Nandina domesticus'', since ''Nandina'' is feminine whereas ''Passer'' is masculine. The tropical fruit Lansium parasiticum, 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, 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 case, genitive (possessive) case. The genitive case is constructed in a number of ways in Latin, depending on the Latin declension, 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 ''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'', where ''coli'' means "of the colon (anatomy), 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. The ''
International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention Convention may refer to: * Convention (norm), a custom or tradition, a standard of presentation or conduct ** Treaty, an agreement in international law * Co ...
'' (''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 name A botanical name is a formal scientific name Science (from the Latin Latin (, ...
'' (''ICNafp'') that of plants (including cyanobacteria), and the ''International Code of Nomenclature of Bacteria'' (''ICNB'') that of bacteria (including Archaea). Virus 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 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 (''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 binomial ''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 wo ...

botany
the starting point will often be in 1753 (the year Carl Linnaeus first published ''
Species Plantarum ' (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, i ...
''). In
zoology Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical stru ...
the starting point is 1758 (1 January 1758 is considered the date of the publication of Linnaeus's ''
Systema Naturae ' (originally in Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Rom ...
'', 10th Edition, and also Carl Alexander Clerck, 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 clades. 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 of , characterized by and large, complex brains. This has enabled the development of advanced , , and . Humans are highly social and tend to live in complex s composed of many ...

Homo sapiens
''. Generally, the binomial should be printed in a font, 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'' is often referred to as just ''E. coli'', and ''Tyrannosaurus, 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. 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. Some examples: *(Plant) ''
Amaranthus retroflexus ''Amaranthus retroflexus'' is a species of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family (biology), f ...
'' L. – "L." is the standard abbreviation for "Linnaeus"; the absence of parentheses shows that this is his original name. *(Plant) ''
Hyacinthoides italica ''Hyacinthoides italica'', the Italian bluebell or Italian squill, is a spring-flowering bulbous perennial plant belonging to the family Asparagaceae Asparagaceae is a Family (biology), family of flowering plants, placed in the Order (biology) ...

Hyacinthoides italica
'' (L.) Rothm. – Linnaeus first named the Italian bluebell ''Scilla italica''; that is the basionym. Werner Hugo Paul Rothmaler, Rothmaler later transferred it to the genus ''Hyacinthoides''. *(Animal) ''
Passer domesticus The house sparrow (''Passer domesticus'') and also known as the common bird or the common sparrow is a bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless ...

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 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 * Botanical name * Hybrid name (botany) * List of botanists by author abbreviation * List of Latin and Greek words commonly used in systematic names * List of organisms named after famous people * List of zoologists by author abbreviation * Scientific terminology * Species description * Undescribed taxon


Notes


References


Bibliography

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External links


Curiosities of Biological Nomenclature

NCBI Taxonomy Database
* {{authority control Biological nomenclature, *