Opisthobranchia vs subclass Opisthobranchia

Opisthobranchia and subclass Opisthobranchia both are nouns.

Word	Noun	Adjective	Verb	Adverb
Opisthobranchia	Yes	No	No	No
subclass Opisthobranchia	Yes	No	No	No

As nouns, Opisthobranchia and subclass Opisthobranchia are synonyms defined as:

Opisthobranchia and subclass Opisthobranchia: gastropods having the gills when present posterior to the heart and having no operculum: includes sea slugs, sea butterflies, sea hares

Opisthobranchia (noun)	subclass Opisthobranchia (noun)
gastropods having the gills when present posterior to the heart and having no operculum: includes sea slugs, sea butterflies, sea hares	gastropods having the gills when present posterior to the heart and having no operculum: includes sea slugs, sea butterflies, sea hares