difficulty vs the devil

difficulty and the devil both are nouns.

Word	Noun	Adjective	Verb	Adverb
difficulty	Yes	No	No	No
the devil	Yes	No	No	No

As nouns, the devil is a hyponym of difficulty; that is, the devil is a word with a more specific, narrower meaning than difficulty:

Other hyponyms of difficulty include tsuris.

difficulty (noun)	the devil (noun)
an effort that is inconvenient	something difficult or awkward to do or deal with
the quality of being almost beyond one's ability to deal with and requiring a great effort to achieve a positive result