gangdom vs Black Hand

gangdom and Black Hand both are nouns.

Word	Noun	Adjective	Verb	Adverb
gangdom	Yes	No	No	No
Black Hand	Yes	No	No	No

As nouns, Black Hand is a hyponym of gangdom; that is, Black Hand is a word with a more specific, narrower meaning than gangdom:

gangdom: underworld organizations
Black Hand: a secret terrorist society in the United States early in the 20th century

Other hyponyms of gangdom include yakuza, Maffia, Mafia, Sicilian Mafia, Camorra, crime syndicate, family, mob, syndicate.

gangdom (noun)	Black Hand (noun)
underworld organizations	a secret terrorist society in the United States early in the 20th century