For the science of classifying living things, see alpha taxonomy.

Taxonomy is the practice and science of classification. The word comes from the Greek τάξις 'order' + νόμος 'law' or 'science'.

Originally the term only referred to the science of classifying living organisms, now called specifically alpha taxonomy; however, the term is now applied in a wider sense and now may refer either to a classification of things, or to the principles underlying that classification.

Almost anything, animate objects, inanimate objects, places, concepts, and events, may be classified according to some taxonomic scheme. Taxonomies, which are composed of taxonomic units known as taxa (singular taxon), are frequently hierarchical in structure, commonly displaying parent-child relationships.

The term taxonomy may also apply to relationship schemes other than hierarchies, such as network structures. Other taxonomies may include single children with multi-parents, for example, "Car" might appear with both parents "Vehicle" and "Steel Mechanisms"; to some however, this merely means that 'car' is part of several different taxonomies. A taxonomy might also be a simple organization of objects into groups, or even an alphabetical list. In current usage within "Knowledge Management", taxonomies are seen as slightly less broad than ontologies.

Mathematically, a hierarchical taxonomy is a tree structure of classifications for a given set of objects. It is also named Containment hierarchy. At the top of this structure is a single classification, the root node, that applies to all objects. Nodes below this root are more specific classifications that apply to subsets of the total set of classified objects. So for instance, in common schemes of scientific classification of organisms, the root is called "Organism" followed by nodes for the ranks: Domain, Kingdom, Phylum, Class, etc. (more details below).

Taxonomy and mental classification

Some have argued that the human mind naturally organizes its knowledge of the world into such systems. This view is often based on the epistemology of Immanuel Kant. Anthropologists have observed that taxonomies are generally embedded in local cultural and social systems, and serve various social functions. Perhaps the most well-known and influential study of folk taxonomies is Émile Durkheim's The Elementary Forms of Religious Life. The theories of Kant and Durkheim also influenced Claude Lévi-Strauss, the founder of anthropological structuralism. Lévi-Strauss wrote two important books on taxonomies, Totemism and The Savage Mind.

Various taxonomies

In alpha taxonomy, as the scientific classification of organisms, the system includes the root called "Organism" (as this applies to all living things, it is implied rather than stated explicitly), followed by the ranks: Domain, Kingdom, Phylum (plural, phyla), Class, Order, Family, Genus, and Species, with over 40 various other ranks sometimes inserted, [1] such as subphylum, superorder, subfamily, subtribe, or subspecies to handle complex groups such as insects (more at: scientific classification or Linnaean taxonomy).

In cladistic taxonomy (or cladism or cladistics), life forms or living organisms can be classified by clades, which are based on evolutionary grouping by ancestoral traits. By using clades as the criteria for separation, cladistic taxonomy, using cladograms, can categorize species into other groups besides the ranks of class, order, family, etc. of Linnean taxonomy.

Other taxonomies, such as those analyzed by Durkheim and Lévi-Strauss, are sometimes called folk taxonomies to distinguish them from scientific taxonomies that claim to be disembedded from social relations and thus objective and universal.

The neologism folksonomy should not be confused with "folk taxonomy" (though it is obviously a contraction of the two words). Those who support scientific taxonomies have recently criticized folksonomies by dubbing them "fauxonomies" (French word "faux" means "false").

The phrase "enterprise taxonomy" is used in business to describe a very limited form of taxonomy used only within one organization.

In numerical taxonomy or taximetrics, the field of solving or best-fitting of numerical equations that characterize all measurable quantities of a set of objects is called cluster analysis.

See also


  1. Common mnemonic devices used for Kingdom-Phylum-Class, etc. include: "King Phillip Came Over From Greece Singing," "King Phillip Came Over From Germany Saturday," "King Phillip Came Over For Good Soup," and "Keep Ponds Clean Or Frogs Grow Scarce," "King Phillip Came Over For Great Spagettii," and "King Phillip Came Over For Good Sex" or in America, "Kenneth Plays Chess On Friday" (+genus species).

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