1. The classification of organisms in an ordered system that indicates natural relationships.
2. The science, laws, or principles of classification; systematics.
3. Division into ordered groups or categories: "Scholars have been laboring to develop a taxonomy of young killers" (Aric Press).

[French taxonomie : Greek taxis, arrangement; see taxis + -nomie, method (from Greek -nomiā; see -nomy).]

Taxonomy of Life

The taxonomic organization of species is hierarchical. Each species belongs to a genus, each genus belongs to a family, and so on through order, class, phylum, and kingdom. Associations within the hierarchy reflect evolutionary relationships, which are deduced typically from morphological and physiological similarities between species. So, for example, species in the same genus are more closely related and more alike than species that are in different genera within the same family. Carolus Linnaeus, an 18th-century Swedish botanist, devised the system of binomial nomenclature used for naming species. In this system, each species is given a two-part Latin name, formed by appending a specific epithet to the genus name. By convention, the genus name is capitalized, and both the genus name and specific epithet are italicized, for Canis familiaris or simply C. familiaris. Modern taxonomy is currently in flux, and certain aspects of classification are being refined. This table shows one traditional classification of five species of life out of the estimated five million species of the world.

Copyright © 2000 by Houghton Mifflin Company

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.