pastoral vs opus

pastoral and opus both are nouns.

Word	Noun	Adjective	Verb	Adverb
pastoral	Yes	Yes	No	No
opus	Yes	No	No	No

As nouns, opus is a hypernym of pastoral; that is, opus is a word with a broader meaning than pastoral:

Other hypernyms of pastoral include composition, musical composition, piece, piece of music.

pastoral (noun)	opus (noun)
a musical composition that evokes rural life	a musical work that has been created
a literary work idealizing the rural life (especially the life of shepherds)
a letter from a pastor to the congregation

pastoral (adjective)	opus (adjective)
of or relating to a pastor
relating to shepherds or herdsmen or devoted to raising sheep or cattle
(used with regard to idealized country life) idyllically rustic