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A taxonomic kingdom is a major taxonomic rank conventionally below a domain and above a taxonomic phylum. A kingdom is a particular taxon at that rank, while the rank word identifies its place in a classification. In a familiar classification of eukaryotes, animals and plants belong to different kingdoms within the same domain.^[ref]

Nested membership permits several descriptions of one organism. An individual animal can belong to the eukaryotic domain, the animal kingdom and a particular phylum simultaneously. The levels select different scales of grouping, rather than offering competing identifications.

A constructed classification database illustrates the information supplied by parent relationships. Suppose kingdom A contains phyla P and Q, with 8 and 12 recorded species, while kingdom B contains phylum R with 20 recorded species. Both kingdom totals are twenty, but A's records are divided between two phyla and B's are not. A query grouped only by kingdom loses that distribution. The counts describe the stipulated records, not a census of complete biological diversity.

The kingdom rank does not prescribe a fixed number of phyla or a particular evolutionary age. Nor does sharing that rank establish equal evolutionary distance between any two groups. A phylogenetic tree represents hypotheses about ancestry and branching; a ranked classification assigns names to selected groupings.^[ref] Keeping the rank, the membership and the supporting evidence separate makes comparisons across classifications more interpretable.

A taxonomic phylum is a major taxonomic rank conventionally below a taxonomic kingdom and above a taxonomic class. A particular phylum is a taxon at that rank. For example, chordates form the phylum containing Mammalia, which in turn contains orders such as Carnivora.^[ref]

The same animal can consequently belong to a phylum, a class and an order without these being competing identifications. Each level adds information about nested membership. The rank word phylum identifies a position in the hierarchy; the group name identifies which taxon occupies that position.

For a constructed survey example, suppose one phylum is represented by four sampled classes with 3, 7, 2 and 8 sampled species. Its total is $3+7+2+8=20$. A second phylum with two sampled classes containing ten species each has the same total. Reporting only twenty species for each phylum loses the class-level distribution, and neither count establishes the total diversity of the unsampled phylum.

A taxonomic rank does not itself specify a fixed age, number of constituent groups or numerical genetic distance. A phylogenetic tree addresses evolutionary relationships, while ranked names select particular groupings for classification.^[ref] The usefulness of the rank comes from organizing comparisons; the scientific interpretation still depends on what was sampled and the evidence supporting membership.