blues vs folk ballad

blues and folk ballad both are nouns.

Word	Noun	Adjective	Verb	Adverb
blues	Yes	No	No	No
folk ballad	Yes	No	No	No

As nouns, folk ballad is a hypernym of blues; that is, folk ballad is a word with a broader meaning than blues:

blues: a type of folksong that originated among Black Americans at the beginning of the 20th century; has a melancholy sound from repeated use of blue notes
folk ballad: a song that is traditionally sung by the common people of a region and forms part of their culture

Other hypernyms of blues include African-American music, black music, folk song, folksong.

blues (noun)	folk ballad (noun)
a type of folksong that originated among Black Americans at the beginning of the 20th century; has a melancholy sound from repeated use of blue notes	a song that is traditionally sung by the common people of a region and forms part of their culture
a state of depression