Nomenclature – Binomial, Trinomial, Rules and Need of Binomial Nomenclature

Binomial Nomenclature is a system of naming biological organism and there are specific rules for naming.

In this article, you would learn everything about Biological Nomenclature. Let us now know about this interesting topic of biology in more detail.

The naming of the species and other higher categories of any recognized system of classification is called Nomenclature.


Scientific names are the language of biologists. When a scientist identifies and describes a taxon or groups of organisms, e.g., a species, he gives a suitable scientific name to the concerned group.

The use of native or common names often creates confusion. Very often, a particular organism has different names in different regions of the world.

For example, the common house sparrow is called gauriaya in India, house sparrow in Britain and Suzune in Japan and so on. Moreover, a particularly common name may also be used for more than one organism. For example, the word ‘worm’ is used for earthworm, nematodes and caterpillar larvae of insects.

Binomial Nomenclature Definition

Bi-meant two, nomial- means names and nomenclature is the process of giving scientific names to animals and plants.

Carolus Linnaeus had established binomial nomenclature.

Once an organism is identified, it is usually given a name by which it can be referred to. Such a nomenclature consists of two words: the first word is the generic name i. e., the name of the genus and the second one is the specific name i. e.. the name of the species.

These words convey definite information about the organism.

The way of naming the animals scientifically is known as zoological nomenclature. For example, the scientific name of the human being is Homo sapiens.

The word Homo is the generic name and sapiens is the name of the species.

These are Latin words and are printed in Italics. Latin was employed because it was the universal language of the educated classes in Europe. A generic name has a capital initial letter and a specific name, a small letter.

When both the names are written, they should be underlined in written scripts. The binomial nomenclature of Linnaeus has become widely accepted in the modern system of classification.

What is the need of Binomial Nomenclature?

This is necessary because the same animal is known by different local names in different countries, states and localities.

The scientific convention, therefore, is that all animal names shall be either in Latin or Greek and that the names shall be the same for the people of all languages throughout the world.

It can be stated in other words:

  1. Common names have different meaning to various persons even in the same part of the country.
  2. Scientific names are uniform internationally and being Latin, are always written in Latin scripts (Italics).

What is Trinomial Nomenclature?

Sometimes the individuals of a species have slight but constant structural differences in which case the particular species is divided into subspecies or varieties.

When sub-species are recognised, their biological names become trinomial one i.e. consisting of three names e.g., generic name, the specific name and sub-specific name.

For example, to distinguish European sparrow from that of the Nile valley, they are named Passer domesticus domesticus and Passer domesticus niloticus respectively.

This system of nomenclature is used in naming subspecies. The subspecies is of a lower category than species. The species of crow is named Corvus splendens. It has three subspecies named as follows:

  • Indian crow: Corvus spenden spendens
  • Myanmar crow: Corvus splendens insolens
  • Crow of Sri Lanka: Corvus spendens protegatus

It is a general practice to write the name of the author immediately after the specific name who first describes that species with year publication, e.g., Homo sapiens (Linnaeus 1758).

Rules of Binomial Nomenclature

In order to avoid confusions in naming and describing a large number of animals and to maintain uniformity throughout the world.

The rules of the nomenclature have been formulated by the International Commission on Zoological nomenclature in 1898 which was formed by the International Zoological Congress.

Some of the rules of Binomial Nomenclature laid down by the Commission are as follows:

  1. No names shall be recognized prior to the one made or accepted by Linnaeus in the tenth edition of his ‘Systema Naturae‘, published in 1758.
  2. New names must be in the customary correct binomial (or trinomial) form and a description of the animal sufficient for identification must have been published for acceptance.
  3. According to the law of priority, the first name proposed for a genus or species shall prevail in case of duplication, provided the above-mentioned conditions have been observed.
  4. All duplicate names are called synonyms. The name of the author who first described the species is put in the last e.g., Panthera tigris (Linnaeus).
  5. The scientific name must be a Latin or Latinized word.
  6. In writing a scientific name, the initial letter of the generic name is always capitalized and that of a specific name and sub-specific name (when such exists) are always in small letters. For example, Rana tigrina is the scientific name of the Indian frog. Here the correct procedure in writing has been followed.
  7. The name of the family is constructed by adding the ending-idae or the name of the sub-family when such exists by adding-inae to the root of the name given to type genus, e.g., Falis- the name of genus–> cat, family–> Felidae
  8. If a new species is established, it is customary to present it in some museum for reference. Such a specimen is called a type specimen.
  9. No two genera of animals may bear the same name this applies to species of any genus also.
  10. The name once published should not normally be changed. 

Some Zoological Names of Common Animals


Common English NameScientific Name
Dog FishScolidion sorrakowah
CatlaCatla catla
RohuLabeo rohita
GiraiOphiocephalus striatus
KauAnabas scandens
MagurClarius batracus


Common NameScientific Name
Common FrogRana tigrina
Green Tree FrogHyla arborea
Flying FrogRhacophorus leucomystax
Indian ToadBufo melanostictus


Common NameScientific Name
Garden LizardCalotes versicolour
House LizardHemidactylus flaviviridis
Russel’s ViperVipera russelli
King CobraNaja bungarus
Common CobraNaja tripudians
Common KraitBungarus coeruleus
Banded KraitBungarus fasciatus
PythonPython molurus
CrocodileCrocodilus palustris
Gavial or Fish Eating CrocodileGavialis gangeticus


Common NameScientific Name
Rock PigeonColumba livia
FowlGallus domesticus
PeacockPavo cristatus
CrowCorvus splendens
ParrotPsittacula eupatria


Common NameScientific Name
House RatRattus rattus
RabbitOryctolagus cuniculus
HareLepus ruficaudatus
Red Faced MonkeyMacaca mulatta
TigerPanthera tigris
LionPanthera leo
LeopardPanthera pardus
Black BearUrsus torquatus
ElephantElephas indica
RhinocerosRhinoceros indicus
HorseEquus caballus
Spotted Deer or CheetalAxis axis
Wild Indian BuffaloBubalis bubalis
Blue Cow (Nilgai)Boselaphus tragocamelus
Domestic CatFelis domestica
Monkey Semnopithecus entellus
ManHomo sapiens

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