Binomial nomenclature
Overview
 
Binomial nomenclature is a formal system of naming species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of living things by giving each a name composed of two parts, both of which use Latin grammatical forms
Latin grammar
The grammar of Latin, like that of other ancient Indo-European languages, is highly inflected; consequently, it allows for a large degree of flexibility in choosing word order...

, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just "binomial"), a binomen or a scientific name; more informally it is also called a Latin name. The first part of the name identifies the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 to which the species belongs; the second part identifies the species within the genus.
Encyclopedia
Binomial nomenclature is a formal system of naming species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of living things by giving each a name composed of two parts, both of which use Latin grammatical forms
Latin grammar
The grammar of Latin, like that of other ancient Indo-European languages, is highly inflected; consequently, it allows for a large degree of flexibility in choosing word order...

, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just "binomial"), a binomen or a scientific name; more informally it is also called a Latin name. The first part of the name identifies the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 to which the species belongs; the second part identifies the species within the genus. For example, humans belong to the genus Homo and within this genus to the species Homo sapiens. The introduction of this system of naming species is credited to Linnaeus, effectively beginning with his work Species Plantarum
Species Plantarum
Species Plantarum was first published in 1753, as a two-volume work by Carl Linnaeus. Its prime importance is perhaps that it is the primary starting point of plant nomenclature as it exists today. This means that the first names to be considered validly published in botany are those that appear...

in 1753. Linnaeus called his two-part name a trivial name (nomen triviale) as opposed to the much longer names then used.

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
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...

(ICZN) for animals and the International Code of Botanical Nomenclature (ICBN) for plants. Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules.

In modern usage, in writing the first letter of the first part of the name, the genus, is always capitalized, while that of the second part is not, even when derived from a proper noun
Proper noun
A proper noun or proper name is a noun representing a unique entity , as distinguished from a common noun, which represents a class of entities —for example, city, planet, person or corporation)...

 such as the name of a person or place. Both parts are italicized. Thus the binomial name of the annual phlox is now written as Phlox drummondii
Phlox drummondii
Phlox drummondii is a flowering plant in the genus Phlox. This plant is native to Texas, but is widely distributed in the southeastern United States, especially along public highways. P. drummondii is often used as an ornamental plant. According to J. P...

.

In scientific works, the "authority" for a binomial name is usually given, at least when it is first mentioned. Thus zoologists will give the name of a particular sea snail species as "Patella vulgata
Patella vulgata
Patella vulgata, colloquially known as the common limpet or Common European Limpet is an edible species of sea snail with gills, a typical true limpet, a marine gastropod mollusc in the family Patellidae. It is endemic to the waters off western Europe.-References:* Lespinet, Nederbragt, Cassan,...

Linnaeus, 1758". The name "Linnaeus" tells the reader who it was that named the species; 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
Systema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...

. (Botanists are not required to give the date).

History

Prior to the adoption of the modern binomial system of naming species, those who wrote about animals and plants either used their common names in various languages or adopted more-or-less standardized descriptions. In medieval Europe these descriptions were typically in Latin, which was then the language of science. Such "polynomial names" may sometimes look like binomials, but are significantly different. For example, Gerard's herbal 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, Soone Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels. The problem was that as new species were discovered, their descriptions needed to become ever longer in order to distinguish them from existing species. For example, the tomato had the polynomial Solanum caule inermi herbaceo, foliis pinnatis incisis, meaning "the smooth-stemmed herbaceous solanum with incised pinnate leaves".

The Bauhins, in particular Caspar Bauhin
Gaspard Bauhin
Gaspard Bauhin, or Caspar Bauhin , was a Swiss botanist who wrote Pinax theatri botanici , which described thousands of plants and classified them in a manner that draws comparisons to the later binomial nomenclature of Linnaeus...

 (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
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 botanist and physician
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 Carl von Linné, more commonly known by his Latinized name Carolus Linnaeus
Carolus Linnaeus
Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...

 (1707–1778). It has been said that the spread of two-part names was in some sense an accident. Linnaeus attempted to describe and classify the entire known natural world. He continued to use polynomial names, but in his Species Plantarum (1753) and later in the 10th edition of Systema Naturae (1758), he supplemented these by what he called a "trivial name" (nomen triviale). The Bauhins' genus names were used in many of these, but the descriptive part was always 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 did not 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
Tradescantia virginiana is a species of Tradescantia native to the eastern United States. Spiderwort is commonly grown in gardens and many garden spiderworts seem to be hybrids of T...

, where the genus name honoured John Tradescant the younger
John Tradescant the younger
John Tradescant the Younger , son of John Tradescant the elder, was a botanist and gardener, born in Meopham, Kent and educated at The King's School, Canterbury...

, an English botanist and gardener. A bird in the parrot family was named Psittacus alexandri
Red-breasted Parakeet
The Red-breasted parakeet, Psittacula alexandri, is among the more widespread species of the genus and is the species which has the most geographical variations. It is easily identified by the large reddish patch on its breast. An alternative name is the Moustached Parakeet depending on subspecies...

, 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.

Value

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
    Family name
    A family name is a type of surname and part of a person's name indicating the family to which the person belongs. The use of family names is widespread in cultures around the world...

     plus given name
    Given name
    A given name, in Western contexts often referred to as a first name, is a personal name that specifies and differentiates between members of a group of individuals, especially in a family, all of whose members usually share the same family 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.
  • Clarity. Binomial names avoid the confusion that can be created when attempting to use common names to refer to a species. Common names often differ even from one part of a country to another, and certainly vary from one country to another. In English-speaking parts of Europe, the bird called a "robin" is Erithacus rubecula
    European Robin
    The European Robin , most commonly known in Anglophone Europe simply as the Robin, is a small insectivorous passerine bird that was formerly classed as a member of the thrush family , but is now considered to be an Old World flycatcher...

    . In English-speaking North America, a "robin" is Turdus migratorius
    American Robin
    The American Robin or North American Robin is a migratory songbird of the thrush family. It is named after the European Robin because of its reddish-orange breast, though the two species are not closely related, with the European robin belonging to the flycatcher family...

    . In contrast, the scientific name can be used all over the world, in all languages, avoiding confusion and difficulties of translation.
  • Uniqueness. Provided that taxonomists agree as to the limits of a species, there can only be one name for it that is correct under the various nomenclature codes, 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 a difficult task, particularly if the species were named by biologists from different countries, so that in reality, a species may have more than one regularly used name (these are "synonyms
    Synonym (taxonomy)
    In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...

    ").
  • Stability. Although stability is far from absolute, the procedures associated with establishing binomial names tend to favor stability. For example, when species are transferred between genera (as not uncommonly happens as a result of new knowledge), if possible the second part of the binomial is kept the same. Thus there is disagreement among botanists as to whether the genera Chionodoxa
    Chionodoxa
    Chionodoxa ' is a small genus of bulbous perennials in the family Asparagaceae, subfamily Scilloideae. The genus is endemic to the eastern Mediterranean region, specifically Crete, Cyprus and Turkey. The blue, white or pink flowers appear early in the year making them valuable garden ornamentals...

    and Scilla
    Scilla
    Scilla is a genus of about 50 bulb-forming perennial herbs in the family Asparagaceae, subfamily Scilloideae, native to woodlands, subalpine meadows, and seashores throughout Europe and Asia...

    are sufficiently different to be kept separate. Those who keep them separate give the plant commonly grown in gardens in Europe the name Chionodoxa siehei
    Chionodoxa siehei
    Chionodoxa siehei or Siehe's Glory-of-the-Snow is a bulbous perennial from west Turkey flowering in early spring. After flowering, it goes into dormancy until the next spring. It seeds readily to form colonies.-Description:...

    ; 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, where possible, retained as 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. Since taxonomists can legitimately disagree as to whether two genera or two species are distinct or not, more than one name can be in use.

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 and/or differences; in biological classification
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....

, 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. The independence is only partial since the names of families and other higher taxa are usually based on genera.

Taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 includes both nomenclature and classification. Its first stages (sometimes called "alpha taxonomy
Alpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...

") are concerned with finding, describing and naming species of living or fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 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 different sources, of which Latin is only one. These include:
  • Latin, either classical
    Latin
    Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

     or medieval
    New Latin
    The term New Latin, or Neo-Latin, is used to describe the Latin language used in original works created between c. 1500 and c. 1900. Among other uses, Latin during this period was employed in scholarly and scientific publications...

    . Thus both parts of the binomial name Homo sapiens are Latin words, meaning "wise" (sapiens) "human/man" (Homo).
  • Classical Greek
    Ancient Greek
    Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

    . The genus Rhododendron
    Rhododendron
    Rhododendron is a genus of over 1 000 species of woody plants in the heath family, most with showy flowers...

    was named by Linnaeus from the Greek word ῥοδόδενδρον, itself derived from rhodos, 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 -ον (-on) is converted to the Latin neuter ending -um.
  • Other languages. The second part of the name Erythroxylum coca is derived from the name of the plant in the Quechua
    Quechua languages
    Quechua is a Native South American language family and dialect cluster spoken primarily in the Andes of South America, derived from an original common ancestor language, Proto-Quechua. It is the most widely spoken language family of the indigenous peoples of the Americas, with a total of probably...

     language.
  • Names of people (often naturalists or biologists). The name Magnolia campbellii commemorates two people: Pierre Magnol
    Pierre Magnol
    Pierre Magnol was a French botanist. He was born in the city of Montpellier, where he lived and worked for the biggest part of his life. He eventually became Professor of Botany and Director of the Royal Botanic Garden of Montpellier and even held a seat in the Académie Royale des Sciences de...

    , a French botanist, and Archibald Campbell, a doctor in British India.
  • Names of places. The lone star tick, Amblyomma americanum
    Amblyomma americanum
    Amblyomma americanum, or lone star tick, is a species of tick in the genus Amblyomma. It's average length is 1/4 inch.-Distribution:...

    is widespread in the United States.
  • Other sources. Some binominal names have been constructed from anagram
    Anagram
    An anagram is a type of word play, the result of rearranging the letters of a word or phrase to produce a new word or phrase, using all the original letters exactly once; e.g., orchestra = carthorse, A decimal point = I'm a dot in place, Tom Marvolo Riddle = I am Lord Voldemort. Someone who...

    s or other re-orderings of existing names. Thus the name of the genus Muilla
    Muilla
    The genus Muilla includes three to four species of flowering plants. In the APG III classification system, it is placed in the family Asparagaceae, subfamily Brodiaeoideae. They are native to western North America...

    is derived by reversing the name Allium
    Allium
    Allium is a monocot genus of flowering plants, informally referred to as the onion genus. The generic name Allium is the Latin word for garlic....

    . Names may also be derived from jokes or puns. For example, Ratcliffe described a number of species of Rhinoceros beetle
    Rhinoceros beetle
    The Rhinoceros Beetles or Rhino Beetles are a subfamily of the scarab beetle family . Other common names – some for particular groups of rhino beetles – are for example Hercules beetles, unicorn beetles or horn beetles...

    , 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
Grammatical number
In linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions ....

 noun in the nominative case
Nominative case
The nominative case is one of the grammatical cases of a noun or other part of speech, which generally marks the subject of a verb or the predicate noun or predicate adjective, as opposed to its object or other verb arguments...

. It must be unique within each kingdom
Kingdom (biology)
In biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...

, but can be repeated between kingdoms. Thus Huia recurvata
Huia (plant)
Huia is a genus of extinct vascular plants of the Early Devonian . The genus was first described in 1985 based on fossil specimens from the Posongchong Formation, Wenshan district, Yunnan, China.-Description:...

is an extinct species of plant, found as fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s in Yunnan
Yunnan
Yunnan is a province of the People's Republic of China, located in the far southwest of the country spanning approximately and with a population of 45.7 million . The capital of the province is Kunming. The province borders Burma, Laos, and Vietnam.Yunnan is situated in a mountainous area, with...

, China, whereas Huia masonii
Javan Torrent Frog
The Javan Torrent Frog is a species of frog in the Ranidae family.It is endemic to Indonesia.Its natural habitats are subtropical or tropical moist lowland forests, subtropical or tropical moist montanes, and rivers.-Source:...

is a species of frog found in Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west 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 different forms.
  • The second part of a binomial may be an adjective. The adjective modifies the genus name, and must agree with it in gender
    Grammatical gender
    Grammatical gender is defined linguistically as a system of classes of nouns which trigger specific types of inflections in associated words, such as adjectives, verbs and others. For a system of noun classes to be a gender system, every noun must belong to one of the classes and there should be...

    . Latin has three genders, masculine, feminine and neuter, shown by different endings to nouns and adjectives. The house sparrow
    House Sparrow
    The House Sparrow is a bird of the sparrow family Passeridae, found in most parts of the world. One of about 25 species in the genus Passer, the House Sparrow occurs naturally in most of Europe, the Mediterranean region, and much of Asia...

     has the binomial name Passer domesticus. Here domesticus ("domestic") simply means "associated with the house". The sacred bamboo
    Nandina
    -Description:Nandina domestica commonly known as nandina, heavenly bamboo or sacred bamboo, is a suckering shrub in the Barberry family, Berberidaceae. It is a monotypic genus, with this species as its only member. It is native to eastern Asia from the Himalaya east to Japan.Despite the common...

     is Nandina domestica rather than Nandina domesticus, since Nandina is feminine whereas Passer is masculine. The tropical fruit langsat
    Lansium domesticum
    Lansium domesticum, also known as langsat or lanzones, is a fruit from the family Meliaceae. The plant, which originates from western Southeast Asia. It is the provincial flower for the Indonesian province of South Sumatra.-Names:...

     is a product of the plant Lansium domesticum, 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
    Lion
    The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...

    , which is Panthera leo. Grammatically the noun is said to be in apposition
    Apposition
    Apposition is a grammatical construction in which two elements, normally noun phrases, are placed side by side, with one element serving to define or modify the other. When this device is used, the two elements are 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
    Genitive case
    In grammar, genitive is the grammatical case that marks a noun as modifying another noun...

     (possessive) case. The genitive case is constructed in a number of different ways in Latin, depending on the declension
    Latin declension
    Latin is an inflected language, and as such has nouns, pronouns, and adjectives that must be declined in order to serve a grammatical function. A set of declined forms of the same word pattern is called a declension. There are five declensions, which are numbered and grouped by ending 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
    Tibetan antelope
    The Tibetan antelope or chiru is a medium-sized bovid which is about in height at the shoulder. It is the sole species in the genus Pantholops and is placed in its own subfamily, Pantholopinae...

     Pantholops hodgsonii, the shrub Magnolia hodgsonii
    Magnolia hodgsonii
    Magnolia hodgsonii , known in Chinese as Gai lie mu is a species of Magnolia native to the forests of the Himalaya and southeastern Asia, occurring in Bhutan, southwestern China , northeastern India, northern Myanmar, Nepal, and Thailand...

    , or the Olive-backed Pipit
    Olive-backed Pipit
    The Olive-backed Pipit, Anthus hodgsoni, is a small passerine bird of the pipit genus, which breeds across South, north Central and East Asia, as well as in the northeast of European Russia. It is a long-distance migrant moving in winter to southern Asia and Indonesia...

     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
    Charles Wallace Richmond
    Charles Wallace Richmond was an American ornithologist. He is best remembered for a compilation of the Latin names of birds that is called the Richmond Index.-Life and work:...

    , in honour of Hodgson. Rather than a person, the noun may be related to a place, as with Latimeria chalumnae
    Latimeria chalumnae
    West Indian Ocean coelacanth is a species of coelacanth, known for its vivid blue pigment. It is the better known of the two extant species.-Biological characteristics:...

    , meaning "of the Chalumna River
    Chalumna River
    The Chalumna River is a river in South Africa which empties into the Indian Ocean and is located about 45 km south west of the Buffalo River at East London. Kayser's Beach is situated close by....

    ". A different example of a genitive noun used as the second part of a binomial name is the name of the bacterium Escherichia coli
    Escherichia coli
    Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

    , where coli means "of the colon
    Colon (anatomy)
    The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...

    ". This formation is common in parasites, as in Xenos vesparum
    Xenos vesparum
    Xenos vesparum is an insect species, whose females are permanent entomophagous endoparasites of Polistes paper wasps. They dwell their whole life in the abdomen of the wasp....

    , 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 a kingdom, the second part is quite commonly used in two or more different genera (as is shown by examples of hodgsonii above). The full binomial name must be unique within a kingdom.

Codes

From the mid nineteenth century onwards it became ever more apparent that a body of rules was necessary to govern scientific names. In the course of time these became nomenclature codes
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...

. The International Code of Zoological Nomenclature
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...

(ICZN) governs the naming of animals, the International Code of Botanical Nomenclature (ICBN) that of plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s (including fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 and cyanobacteria), and the International Code of Nomenclature of Bacteria
International Code of Nomenclature of Bacteria
The International Code of Nomenclature of Bacteria or Bacteriological Code governs the scientific names for bacteria, including Archaea. It denotes the rules for naming taxa of bacteria, according to their relative rank...

(ICNB) that of bacteria (including Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

). Virus names are governed by the International Committee on Taxonomy of Viruses
International Committee on Taxonomy of Viruses
The International Committee on Taxonomy of Viruses is a committee which authorizes and organizes the taxonomic classification of viruses. They have developed a universal taxonomic scheme for viruses and aim to describe all the viruses of living organisms. Members of the committee are considered to...

(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.
  • Both codes agree in calling the first part of the two-part name for a species the "genus name". However in zoological nomenclature the second part is called the "species name", whereas in botanical nomenclature the second part is called the "species epithet", and the term "species name" should only be used for the whole name, i.e. the combination of the two parts.
  • The ICBN, the plant Code, does not allow the two parts of a binomial name to be the same (such a name is called a tautonym
    Tautonym
    -In biology :In biology, tautonym is an informal term to indicate a scientific name of a species in which both parts of the name have the same spelling, for example Bison bison...

    ), 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
    Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

     the starting point will often be in 1753 (the year Carl Linnaeus first published Species Plantarum
    Species Plantarum
    Species Plantarum was first published in 1753, as a two-volume work by Carl Linnaeus. Its prime importance is perhaps that it is the primary starting point of plant nomenclature as it exists today. This means that the first names to be considered validly published in botany are those that appear...

    ). In zoology
    Zoology
    Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

     the starting point is 1758 (1 January 1758 is considered the date of the publication of Linnaeus's Systema Naturae
    Systema Naturae
    The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...

    , 10th Edition, and also Clerck's
    Carl Alexander Clerck
    Carl Alexander Clerck was a Swedish entomologist and arachnologist.Clerck came from a family in the petty nobility and entered the University of Uppsala in 1726. Little is known of his studies; although a contemporary of Linnaeus, it is unknown whether he had any contact with him during his time...

     Aranei Svecici). Bacteriology
    Bacteriology
    Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

     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 code in development for a different system of classification which does not use ranks, but instead names clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

s. This is called the PhyloCode
PhyloCode
The International Code of Phylogenetic Nomenclature, known as the PhyloCode for short, is a developing draft for a formal set of rules governing phylogenetic nomenclature...

.)

Writing binomial names

The binomial names of species are usually typeset in italics; for example, Homo sapiens. Generally the binomial should be printed in a font
Font
In typography, a font is traditionally defined as a quantity of sorts composing a complete character set of a single size and style of a particular typeface...

 different from that used in the normal text; for example, "Several more Homo sapiens fossils were discovered." When handwritten, each part of 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. 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 "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
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

is often referred to as just E. coli, and Tyrannosaurus rex
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...

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
Canis
Canis is a genus containing 7 to 10 extant species, including dogs, wolves, coyotes, and jackals, and many extinct species.-Wolves, dogs and dingos:Wolves, dogs and dingos are subspecies of Canis lupus...

", while "Canis spp." means "two or more species of the genus Canis". (The abbreviations "sp." and "spp." can easily be confused with the abbreviations "ssp." (zoology) or "subsp." (botany), plurals "sspp." or "subspp.", referring to one or more subspecies. See trinomen
Trinomen
In zoological nomenclature, a trinomen , or trinominal name, refers to the name of a subspecies.A trinomen is a name consisting of three names: generic name, specific name and subspecific name. The first two parts alone form the binomen or species name. All three names are typeset in italics, and...

 (zoology) and infraspecific name (botany)
Infraspecific name (botany)
In botany, an infraspecific name is the name for any taxon below the rank of species, i.e. an infraspecific taxon. The scientific names of plants are regulated by the International Code of Botanical Nomenclature...

.)

The abbreviation "cf.
Cf.
cf., an abbreviation for the Latin word confer , literally meaning "bring together", is used to refer to other material or ideas which may provide similar or different information or arguments. It is mainly used in scholarly contexts, such as in academic or legal texts...

" is used when the identification is not confirmed. For example "Corvus cf. splendens" indicates "a bird similar to the house crow
House Crow
thumb|300px|Bangalore, IndiaThe House Crow , also known as the Colombo Crow is a common bird of the Crow family that is of Asian origin but now found in many parts of the world, where they arrived assisted by shipping. It is between the Jackdaw and the Carrion Crow in size but is relatively...

 but not certainly identified as this species".

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: under the ICZN the surname is written in full together with the date (usually only the year) of publication, whereas under the ICBN the name is generally abbreviated and the date omitted. 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 ICBN also requires the person who made the change to be given. Some examples:
  • (plant) Amaranthus retroflexus
    Amaranthus retroflexus
    Amaranthus retroflexus is a species of flowering plant in the Amaranthaceae family with several common names, including Red-root Amaranth, Redroot Pigweed, Red Rooted Pigweed, Common Amaranth, and common tumble weed....

    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; Rothmaler transferred it to the genus Hyacinthoides.
  • (animal) Passer domesticus (Linnaeus, 1758) – the original name given by Linnaeus was Fringilla domestica; unlike the ICBN, 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 ICBN. In zoology, the only rank below species is subspecies and the name is written simply as three parts. Thus one of the subspecies of the olive-backed pipit
Olive-backed Pipit
The Olive-backed Pipit, Anthus hodgsoni, is a small passerine bird of the pipit genus, which breeds across South, north Central and East Asia, as well as in the northeast of European Russia. It is a long-distance migrant moving in winter to southern Asia and Indonesia...

 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
Cyclamen hederifolium
Cyclamen hederifolium is the most widespread cyclamen species, the most widely cultivated after the florist's cyclamen , and the most hardy and vigorous in oceanic climates...

f. albiflorum.

See also

  • Botanical name
    Botanical name
    A botanical name is a formal scientific name conforming to the International Code of Botanical Nomenclature and, if it concerns a plant cultigen, the additional cultivar and/or Group epithets must conform to the International Code of Nomenclature for Cultivated Plants...

     (in botany)
  • Hybrid name
    Hybrid name
    In botanical nomenclature, a hybrid may be given a hybrid name, which is a special kind of botanical name. The ICBN provides the following options in dealing with a hybrid:...

  • List of botanists by author abbreviation
  • List of zoologists by author abbreviation
  • Species description
    Species description
    A species description or type 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 which have been described previously, or are...


External links

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