gentry vs upper class

gentry and upper class both are nouns.

Word	Noun	Adjective	Verb	Adverb
gentry	Yes	No	No	No
upper class	Yes	No	No	No

As nouns, upper class is a hypernym of gentry; that is, upper class is a word with a broader meaning than gentry:

gentry: the most powerful members of a society
upper class: the class occupying the highest position in the social hierarchy

Other hypernyms of gentry include upper crust.

gentry (noun)	upper class (noun)
the most powerful members of a society	the class occupying the highest position in the social hierarchy