demon vs monster

demon and monster both are nouns.

Word	Noun	Adjective	Verb	Adverb
demon	Yes	No	No	No
monster	Yes	No	No	No

As nouns, demon and monster are synonyms defined as:

Other synonyms of demon include devil, fiend, ogre.

demon (noun)	monster (noun)
an evil supernatural being	(medicine) a grossly malformed and usually nonviable fetus
a cruel wicked and inhuman person	a cruel wicked and inhuman person
someone extremely diligent or skillful	a person or animal that is markedly unusual or deformed
	an imaginary creature usually having various human and animal parts
	someone that is abnormally large and powerful