= Taxonomic kingdom
A <taxonomic kingdom> is a major <taxonomic rank> conventionally below a <domain (biology)> 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.<Biology 2e by Mary Ann Clark and others>[section 20.1, Classification Levels and Figures 20.5–20.6]{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.<Biology 2e by Mary Ann Clark and others>[section 20.1, Phylogenetic Trees and Classification Levels]{ref} Keeping the rank, the membership and the supporting evidence separate makes comparisons across classifications more interpretable.
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