Nematoda vs phylum

Nematoda and phylum both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nematoda	Yes	No	No	No
phylum	Yes	No	No	No

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

Nematoda: unsegmented worms: roundworms, threadworms, eelworms
phylum: (biology) the major taxonomic group of animals and plants; contains classes

Nematoda (noun)	phylum (noun)
unsegmented worms: roundworms, threadworms, eelworms	(biology) the major taxonomic group of animals and plants; contains classes
	(linguistics) a large group of languages that are historically related