thief vs crook

thief and crook both are nouns.

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

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

thief: a criminal who takes property belonging to someone else with the intention of keeping it or selling it
crook: someone who has committed a crime or has been legally convicted of a crime

Other hypernyms of thief include criminal, felon, malefactor, outlaw.

thief (noun)	crook (noun)
a criminal who takes property belonging to someone else with the intention of keeping it or selling it	a long staff with one end being hook shaped
	someone who has committed a crime or has been legally convicted of a crime
	a circular segment of a curve

thief (verb)	crook (verb)
	bend or cause to bend