gangland vs yakuza

gangland and yakuza both are nouns.

Word	Noun	Adjective	Verb	Adverb
gangland	Yes	No	No	No
yakuza	Yes	No	No	No

As nouns, yakuza is a hyponym of gangland; that is, yakuza is a word with a more specific, narrower meaning than gangland:

gangland: underworld organizations
yakuza: organized crime in Japan; an alliance of criminal organizations and illegal enterprises

Other hyponyms of gangland include Maffia, Mafia, Sicilian Mafia, Black Hand, Camorra, crime syndicate, family, mob, syndicate.

gangland (noun)	yakuza (noun)
underworld organizations	organized crime in Japan; an alliance of criminal organizations and illegal enterprises
	a Japanese gangster