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