ghoul vs thief

ghoul and thief both are nouns.

Word	Noun	Adjective	Verb	Adverb
ghoul	Yes	No	No	No
thief	Yes	No	No	No

As nouns, thief is a hypernym of ghoul; that is, thief is a word with a broader meaning than ghoul:

ghoul: someone who takes bodies from graves and sells them for anatomical dissection
thief: a criminal who takes property belonging to someone else with the intention of keeping it or selling it

Other hypernyms of ghoul include stealer.

ghoul (noun)	thief (noun)
an evil spirit or ghost	a criminal who takes property belonging to someone else with the intention of keeping it or selling it
someone who takes bodies from graves and sells them for anatomical dissection