Binomial Nomenclature - Derivation of Binomial Names

Derivation of Binomial Names

A complete binomial name is always treated grammatically as if it were a phrase in the Latin language (hence the common use of the term "Latin name" for a binomial name). However, the two parts of a binomial name can each be derived from a number of sources, of which Latin is only one. These include:

• Latin, either classical or medieval. Thus both parts of the binomial name Homo sapiens are Latin words, meaning "wise" (sapiens) "human/man" (Homo).
• Classical Greek. The genus Rhododendron 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 often 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 language. Since many dinosaur fossils were found in Mongolia, their names often use Mongolian words, e.g. Tarchia from tarkhi, meaning "brain", or Saichania meaning "beautiful one".
• Names of people (often naturalists or biologists). The name Magnolia campbellii commemorates two people: Pierre Magnol, a French botanist, and Archibald Campbell, a doctor in British India.
• Names of places. The lone star tick, Amblyomma americanum is widespread in the United States.
• Other sources. Some binominal names have been constructed from 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 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.

• The second part of a binomial may be an adjective. The adjective modifies the genus name, and must agree with it in gender. Latin has three genders, masculine, feminine and neuter, shown by varying endings to nouns and adjectives. The house sparrow has the binomial name Passer domesticus. Here domesticus ("domestic") simply means "associated with the house". The sacred bamboo is Nandina domestica rather than Nandina domesticus, since Nandina is feminine whereas Passer is masculine. The tropical fruit langsat 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, which is Panthera leo. Grammatically the noun is said to be in apposition to the genus name and the two nouns do not have to agree in gender; in this case, Panthera is feminine and leo is masculine.
• The second part of a binomial may be a noun in the genitive (possessive) case. The genitive case is constructed in a number of ways in Latin, depending on the declension of the noun. Common endings for masculine and neuter nouns are -ii or -i in the singular and -orum in the plural, and for feminine nouns -ae in the singular and -arum in the plural. The noun may be part of a person's name, often the surname, as in the Tibetan antelope Pantholops hodgsonii, the shrub 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". An example of another use of genitive nouns is the second part of a binomial name is the name of the bacterium Escherichia coli, where coli means "of the colon". This formation is common in parasites, as in Xenos vesparum, where vesparum means "of the wasps", since Xenos vesparum is a parasite of wasps.

Whereas the first part of a binomial name must be unique within 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.