phylum

noun

(Gr. phylę: tribe) A taxon of high rank, the major unit of classification; the five kingdoms are divided into phyla, which in turn each contain a number of classes; in the plant kingdom, it is usually replaced by the division. Examples of phyla are the Rhodophyta, Ascomycota, Bryophyta, Annelida, and Chordata. Organisms belonging to the same phylum share basic features but are divided into classes, orders, genera, and species according to their supposed degrees of relationship. For example, the phylum Arthropoda is a very diverse group including the insects, spiders, scorpions, crustaceans, etc., which all share the features of a tough segmented external skeleton and jointed limbs.