ruralism vs set phrase

ruralism and set phrase both are nouns.

Word	Noun	Adjective	Verb	Adverb
ruralism	Yes	No	No	No
set phrase	Yes	No	No	No

As nouns, set phrase is a hypernym of ruralism; that is, set phrase is a word with a broader meaning than ruralism:

ruralism: a rural idiom or expression
set phrase: an expression whose meanings cannot be inferred from the meanings of the words that make it up

Other hypernyms of ruralism include idiom, idiomatic expression, phrasal idiom, phrase.

ruralism (noun)	set phrase (noun)
a rural characteristic or trait	an expression whose meanings cannot be inferred from the meanings of the words that make it up
a rural idiom or expression
Advocacy of rural life instead of urbanism or city living.