Taxon

A taxon (plural taxa) is an element of a taxonomy, e.g. in the scientific classification in biology. Taxa form a hierarchical scheme, each being broken down into subtaxa.

In traditional Linnaean taxonomy, taxa are ranked as follows:

• Kingdom
• Phylum (animals) or Division (plants)
• Class
• Order
• Family
• Genus
• Species

The prefix super- indicates a rank above another, the prefix sub- indicates a rank below another, and the prefix infra- indicates a rank below sub-. For instance:

• Superclass
• Class
• Subclass
• Infraclass

It has become generally accepted that taxa should contain an ancestral form and all or some of its descendants, though the validity of the latter category is increasingly debated.