Binomial nomenclature ("two-term naming system"), also called binominal 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, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just "binomial"), a binomen, binominal name or a scientific name; more informally it is also called a Latin name.
The first part of the name – the generic name – identifies the genus 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 and within this genus to the species Homo sapiens . Tyrannosaurus rex is probably the most widely known binomial.The formal introduction of this system of naming species is credited to Carl Linnaeus, effectively beginning with his work Species Plantarum in 1753. But Gaspard Bauhin, in as early as 1622, had 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 (ICZN) for animals and the International Code of Nomenclature for algae, fungi, and plants (ICNafp). Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules.
In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not, even when derived from a proper noun such as the name of a person or place. Similarly, both parts are italicized when a binomial name occurs in normal text (or underlined in handwriting). Thus the binomial name of the annual phlox (named after botanist Thomas Drummond) is now written as Phlox drummondii .
In scientific works, the authority for a binomial name is usually given, at least when it is first mentioned, and the date of publication may be specified.
The name is composed of two word-forming elements: bi- (Latin prefix meaning 'two') and nomial (literally 'name'). In Medieval Latin, the related word binomium was used to signify one term in a binomial expression in mathematics.
Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name that was from one to several words long. Together they formed a system of polynomial nomenclature.These names had two separate functions. First, to designate or label the species, and second, to be a diagnosis or description; however these two goals were eventually found to be incompatible. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; but as more species were discovered, the names necessarily became longer and unwieldy, for instance, Plantago foliis ovato-lanceolatus pubescentibus, spica cylindrica, scapo tereti ("plantain with pubescent ovate-lanceolate leaves, a cylindric spike and a terete scape"), which we know today as Plantago media .
Such "polynomial names" may sometimes look like binomials, but are significantly different. For example, Gerard's herbal (as amended by Johnson) describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort; the second, Phalangium non ramosum, Unbranched Spiderwort. The other ... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia".The Latin phrases are short descriptions, rather than identifying labels.
The Bauhins, in particular Caspar Bauhin (1560–1624), took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words.The adoption by biologists of a system of strictly binomial nomenclature is due to Swedish botanist and physician Carl Linnaeus (1707–1778). It was in Linnaeus's 1753 Species Plantarum that he began consistently using a one-word "trivial name" (nomen triviale) 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 (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 , where the genus name honoured John Tradescant the Younger,an English botanist and gardener. A bird in the parrot family was named Psittacus alexandri , meaning "Alexander's parrot", after Alexander the Great, whose armies introduced eastern parakeets to Greece. Linnaeus's trivial names were much easier to remember and use than the parallel polynomial names and eventually replaced them.
The value of the binomial nomenclature system derives primarily from its economy, its widespread use, and the uniqueness and stability of names it generally favors:
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. 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.
Nomenclature (including binomial nomenclature) is not the same as classification, although the two are related. Classification is the ordering of items into groups based on similarities or differences; in biological classification, species are one of the kinds of item to be classified. [ citation needed ]In principle, the names given to species could be completely independent of their classification. This is not the case for binomial names, since the first part of a binomial is the name of the genus into which the species is placed. Above the rank of genus, binomial nomenclature and classification are partly independent; for example, a species retains its binomial name if it is moved from one family to another or from one order to another, unless it better fits a different genus in the same or different family, or it is split from its old genus and placed in a newly created genus. The independence is only partial since the names of families and other higher taxa are usually based on genera.
Taxonomy includes both nomenclature and classification. Its first stages (sometimes called "alpha taxonomy") are concerned with finding, describing and naming species of living or fossil organisms.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.
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:
The first part of the name, which identifies the genus, must be a word which can be treated as a Latin singular noun in the nominative case. It must be unique within each kingdom, but can be repeated between kingdoms. Thus Huia recurvata is an extinct species of plant, found as fossils in Yunnan, China,whereas 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:
Whereas the first part of a binomial name must be unique within a kingdom, the second part is quite commonly used in two or more genera (as is shown by examples of hodgsonii above). The full binomial name must be unique within a kingdom.
From the early 19th century onwards it became ever more apparent that a body of rules was necessary to govern scientific names. In the course of time these became nomenclature codes. The International Code of Zoological Nomenclature (ICZN) governs the naming of animals,the International Code of Nomenclature for algae, fungi, and plants (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.:
|Code||Full name||First part||Second part|
|ICZN||species name, binomen, binominal name||generic name, genus name||specific name|
|ICNafp||species name, binary combination, binomial (name)||generic name||specific epithet|
Unifying the different codes into a single code, the "BioCode", has been suggested, although implementation is not in sight. (There is also a code in development for a different system of classification which does not use ranks, but instead names clades. This is called the PhyloCode .)
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.
By tradition, the binomial names of species are usually typeset in italics; for example, Homo sapiens .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. 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 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" (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 (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.
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:
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Binomial nomenclature, as described here, is a system for naming species. Implicitly it includes a system for naming genera, since the first part of the name of the species is a genus name. In a classification system based on ranks there are also ways of naming ranks above the level of genus and below the level of species. Ranks above genus (e.g., family, order, class) receive one-part names, which are conventionally not written in italics. Thus the house sparrow, Passer domesticus, belongs to the family Passeridae. Family names are normally based on genus names, although the endings used differ between zoology and botany.
Ranks below species receive three-part names, conventionally written in italics like the names of species. There are significant differences between the ICZN and the 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.
Linnaean taxonomy can mean either of two related concepts:
A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.
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 International Commission on Zoological Nomenclature. The rules principally regulate:
In biology, a taxon is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion. If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping.
In biology, a common name of a taxon or organism is a name that is based on the normal language of everyday life; this kind of name is often contrasted with the scientific name for the same organism, which is Latinized. A common name is sometimes frequently used, but that is by no means always the case.
In biology, a type is a particular specimen of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralize the defining features of that particular taxon. In older usage, a type was a taxon rather than a specimen.
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 International Code of Nomenclature for Cultivated Plants (ICNCP). The code of nomenclature covers "all organisms traditionally treated as algae, fungi, or plants, whether fossil or non-fossil, including blue-green algae (Cyanobacteria), chytrids, oomycetes, slime moulds and photosynthetic protists with their taxonomically related non-photosynthetic groups ."
A tautonym is a scientific name of a species in which both parts of the name have the same spelling, for example Rattus rattus. The first part of the name is the name of the genus and the second part is referred to as the specific epithet in the International Code of Nomenclature for algae, fungi, and plants and the specific name in the International Code of Zoological Nomenclature.
In botany, the correct name according to the International Code of Nomenclature for algae, fungi, and plants (ICN) is the one and only botanical name that is to be used for a particular taxon, when that taxon has a particular circumscription, position and rank. Determining whether a name is correct is a complex procedure. The name must be validly published, a process which is defined in no less than 16 Articles of the ICN. It must also be "legitimate", which imposes some further requirements. If there are two or more legitimate names for the same taxon, then the correct name is the one which has priority, i.e. it was published earliest, although names may be conserved if they have been very widely used. Validly published names other than the correct name are called synonyms. Since taxonomists may disagree as to the circumscription, position or rank of a taxon, there can be more than one correct name for a particular plant. These may also be called synonyms.
In zoological nomenclature, the specific name is the second part within the scientific name of a species. The first part of the name of a species is the name of the genus or the generic name. The rules and regulations governing the giving of a new species name are explained in the article species description.
In zoological nomenclature, author citation refers to listing the person who first makes a scientific name of a taxon available. This is done in a scientific publication while fulfilling the formal requirements under the International Code of Zoological Nomenclature, hereinafter termed "the Code". According to the Code, "the name of the author does not form part of the name of a taxon and its citation is optional, although customary and often advisable", however Recommendation 51A suggests: "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. This is especially important in distinguishing between homonyms and in identifying species-group names which are not in their original combinations". For the purpose of information retrieval, the author citation and year appended to the scientific name, e.g. genus-species-author-year, genus-author-year, family-author-year, etc., is often considered a "de facto" unique identifier, although for a number of reasons discussed below, this usage may often be imperfect.
In botanical nomenclature, author citation is the way of citing the person or group of people who validly published a botanical name, i.e. who first published the name while fulfilling the formal requirements as specified by the International Code of Nomenclature for algae, fungi, and plants (ICN). In cases where a species is no longer in its original generic placement, both the authority for the original genus placement and that for the new combination are given.
In biological nomenclature, a nomen novum, new replacement name is a technical term. It indicates a scientific name that is created specifically to replace another scientific name, but only when this other name cannot be used for technical, nomenclatural reasons ; it does not apply when a name is changed for taxonomic reasons. It is frequently abbreviated, e.g.nomen nov., nom. nov..
The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) 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. This name is no longer in use: it is now a synonym of the current scientific name, Picea abies. In zoology, moving a species from one genus to another results in a different binomen, but the name is considered an alternative combination, rather than a synonym. The concept of synonymy in zoology is reserved for two names at the same rank that refer to a taxon at that rank - for example, the name Papilio prorsaLinnaeus, 1758 is a junior synonym of Papilio levanaLinnaeus, 1758, being names for different seasonal forms of the species now referred to as Araschnia levana(Linnaeus, 1758), the map butterfly. However, Araschnia levana is not a synonym of Papilio levana in the taxonomic sense employed by the Zoological code.
Philosophia Botanica was published by the Swedish naturalist and physician Carl Linnaeus (1707–1778) who greatly influenced the development of botanical taxonomy and systematics in the 18th and 19th centuries. It is "the first textbook of descriptive systematic botany and botanical Latin". It also contains Linnaeus's first published description of his binomial nomenclature.
In biological classification, taxonomic rank is the relative level of a group of organisms in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, order, class, phylum, kingdom, domain, etc.
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 which have been described previously or are related. The species description often contains photographs or other illustrations of the type material and states in which museums it has been deposited. The publication in which the species is described gives the new species a formal scientific name. Some 1.9 million species have been identified and described, out of some 8.7 million that may actually exist. Millions more have become extinct throughout the existence of life on Earth.
The book Svenska Spindlar or Aranei Svecici was one of the major works of the Swedish arachnologist and entomologist Carl Alexander Clerck and appeared in Stockholm in the year 1757. It was the first comprehensive book on the spiders of Sweden and one of the first regional monographs of a group of animals worldwide. The full title of the work was Svenska Spindlar uti sina hufvud-slägter indelte samt under några och sextio särskildte arter beskrefne och med illuminerade figurer uplyste – Aranei Svecici, descriptionibus et figuris æneis illustrati, ad genera subalterna redacti, speciebus ultra LX determinati, and included 162 pages of text and 6 colour plates. It was published in Swedish, with a Latin translation printed in a slightly smaller font below the Swedish text.
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 abbreviations are used with or without a stop.