pathos vs fellow feeling

pathos and fellow feeling both are nouns.

Word	Noun	Adjective	Verb	Adverb
pathos	Yes	No	No	No
fellow feeling	Yes	No	No	No

As nouns, fellow feeling is a hypernym of pathos; that is, fellow feeling is a word with a broader meaning than pathos:

pathos: a feeling of sympathy and sorrow for the misfortunes of others
fellow feeling: sharing the feelings of others (especially feelings of sorrow or anguish)

Other hypernyms of pathos include sympathy.

pathos (noun)	fellow feeling (noun)
a quality that arouses emotions (especially pity or sorrow)	sharing the feelings of others (especially feelings of sorrow or anguish)
a style that has the power to evoke feelings
a feeling of sympathy and sorrow for the misfortunes of others