Cnidaria vs class Hydrozoa

Cnidaria and class Hydrozoa both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cnidaria	Yes	No	No	No
class Hydrozoa	Yes	No	No	No

Cnidaria (noun)	class Hydrozoa (noun)
hydras, polyps, jellyfishes, sea anemones, corals	coelenterates typically having alternation of generations; hydroid phase is usually colonial giving rise to the medusoid phase by budding: hydras and jellyfishes