# Taxonomy

Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. Organisms are grouped together into taxa (singular: taxon) and given a taxonomic rank. Groups of a given rank can be aggregated to form a super group of higher rank and thus create a taxonomic hierarchy. The Swedish botanist Carolus Linnaeus is regarded as the father of taxonomy, as he developed a system known as Linnaean classification for categorization of organisms and binomial nomenclature for naming organisms. With the advent of such fields of study as phylogenetics, cladistics, and systematics, the Linnaean system has progressed to a system of modern biological classification based on the evolutionary relationships between organisms, both living and extinct

The term taxonomy is derived from the Ancient Greek word taxis (τάξις) meaning "arrangement" and -nomia (νομία) meaning "method".

Taxon

In biology, a taxon (plural taxa; back-formation from taxonomy) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. A taxon is usually known by a particular name and given a particular ranking.

Taxonomic rank

In biological classification, rank is the level (the relative position) in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class.
Each rank subsumes under it a number of less general categories.
The rank of species, and specification of the genus to which the species belongs is basic, which means that it may not be necessary to specify ranks other than these.
The International Code of Zoological Nomenclature defines rank as:
The level, for nomenclatural purposes, of a taxon in a taxonomic hierarchy (e.g. all families are for nomenclatural purposes at the same rank, which lies between superfamily and subfamily).

Figure: Example of division terms used in Taxonomic rank.

## Related concepts

Cladistics is an approach to biological classification in which organisms are grouped together. This grouping is based on whether or not organisms have one or more shared unique characteristics that come from the group's last common ancestor and are not present in more distant ancestors. Therefore, members of the same group are thought to share a common history and are considered to be more closely related. When these lineage-branching (with regard to common ancestor) are drawn in a diagram, this is called a cladogram.

The term cladistic is derived from the Ancient Greek word klados (κλάδος) meaning "branch".

### Phylogenetic nomenclature

Phylogenetic nomenclature, often called cladistic nomenclature, is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names. This contrasts with the traditional approach, in which taxon names are defined by a type, which can be a specimen or a taxon of lower rank, and a diagnosis, a statement intended to supply characters that differentiate the taxon from others with which it is likely to be confused. Phylogenetic nomenclature is currently not regulated, but the International Code of Phylogenetic Nomenclature (PhyloCode) is intended to regulate it once it is ratified.