taxonomy -
The science of finding, describing, classifying and naming organisms.
Wikipedia
Taxonomy is the practice and science of classification. The word finds its roots in the Greek τάξις, taxis (meaning 'order' or 'arrangement') and νόμος, nomos (meaning 'law' or 'science'). Taxonomy uses taxonomic units, known as taxa.
OmegaWiki Dictionary
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taxonomy The branch of biology concerned with the classification of organisms into groups based on similarities of structures, origin, etc.
taxonomy A hierarchical organization of a subject area, from one perspective in one language.