gangster vs crook

gangster and crook both are nouns.

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

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

gangster: a criminal who is a member of gang
crook: someone who has committed a crime or has been legally convicted of a crime

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

gangster (noun)	crook (noun)
a criminal who is a member of gang	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

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