gangster vs criminal

gangster and criminal both are nouns.

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

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

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

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

gangster (noun)	criminal (noun)
a criminal who is a member of gang	someone who has committed a crime or has been legally convicted of a crime

gangster (adjective)	criminal (adjective)
	guilty of crime or serious offense
	involving or being or having the nature of a crime
	bringing or deserving severe rebuke or censure