fiend vs devil

fiend and devil both are nouns.

Word	Noun	Adjective	Verb	Adverb
fiend	Yes	No	No	No
devil	Yes	No	Yes	No

As nouns, fiend and devil are synonyms defined as:

Other synonyms of fiend include demon, monster, ogre.

As nouns, fiend and devil are synonyms defined as:

Other synonyms of fiend include daemon, daimon, demon.

fiend (noun)	devil (noun)
a cruel wicked and inhuman person	a word used in exclamations of confusion
a person motivated by irrational enthusiasm (as for a cause)	an evil supernatural being
an evil supernatural being	a cruel wicked and inhuman person
	a rowdy or mischievous person (usually a young man)

fiend (verb)	devil (verb)
	coat or stuff with a spicy paste
	cause annoyance in; disturb, especially by minor irritations