From The Art and Popular Culture Encyclopedia
In biology, a phylum (plural: phyla) is a taxonomic rank below Kingdom and above Class. "Phylum" is equivalent to the botanical term division. Phylum is one of the major biological divisions called Taxa. Although "phylum" is often used as if it were a clearly defined term, no satisfactory definition of it exists. In fact, "phylum" may be a misnomer indicative of ignorance. Consequently the number of phyla varies from one author to the next. The relationships among phyla are becoming increasingly well known, and larger clades can be found to contain many of the phyla.