Taxonomy is the science

Science

Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...

 of identifying and naming species, and arranging them into a classification

Classification

Classification may refer to:* Library classification and classification in general* Taxonomic classification * Biological classification of organisms* Medical classification* Scientific classification...

. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa (singular taxon

Taxon

|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

). A resulting taxonomy is a particular classification ("the taxonomy of ..."), arranged in a hierarchical

Hierarchy

A hierarchy is an arrangement of items in which the items are represented as being "above," "below," or "at the same level as" one another...

 structure or classification scheme

Classification scheme

In metadata a classification scheme is a hierarchical arrangement of kinds of things or groups of kinds of things. Typically it is accompanied by descriptive information of the classes or groups. A classification scheme is intended to be used for an arrangement or division of individual objects...

. An example of a modern classification is the one published in 2009 by the Angiosperm Phylogeny Group

Angiosperm Phylogeny Group

The Angiosperm Phylogeny Group, or APG, refers to an informal international group of systematic botanists who came together to try to establish a consensus on the taxonomy of flowering plants that would reflect new knowledge about plant relationships discovered through phylogenetic studies., three...

 for all living flowering plant

Flowering plant

The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

 families (the APG III system

APG III system

The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy...

).
The exact definition of taxonomy varies slightly from source to source, but the core of the discipline remains: the identification, naming, and classifying of organisms. As points of reference, three recent textbook definitions are presented below:

1. Theory and practice of grouping individuals into species, arranging species into larger groups, and giving those groups names, thus producing a classification (Judd et al., 2007)
2. A field of science (and major component of systematics) that encompasses description, identification, nomenclature, and classification.