subphylum Urochordata vs phylum

subphylum Urochordata and phylum both are nouns.

Word	Noun	Adjective	Verb	Adverb
subphylum Urochordata	Yes	No	No	No
phylum	Yes	No	No	No

As nouns, phylum is a hypernym of subphylum Urochordata; that is, phylum is a word with a broader meaning than subphylum Urochordata:

subphylum Urochordata: tunicates
phylum: (biology) the major taxonomic group of animals and plants; contains classes

subphylum Urochordata (noun)	phylum (noun)
tunicates	(biology) the major taxonomic group of animals and plants; contains classes
	(linguistics) a large group of languages that are historically related