Sicilian Mafia vs gangland

Sicilian Mafia and gangland both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sicilian Mafia	Yes	No	No	No
gangland	Yes	No	No	No

As nouns, gangland is a hypernym of Sicilian Mafia; that is, gangland is a word with a broader meaning than Sicilian Mafia:

Sicilian Mafia: a secret terrorist group in Sicily; originally opposed tyranny but evolved into a criminal organization in the middle of the 19th century
gangland: underworld organizations

Other hypernyms of Sicilian Mafia include gangdom, organized crime.

Sicilian Mafia (noun)	gangland (noun)
a secret terrorist group in Sicily; originally opposed tyranny but evolved into a criminal organization in the middle of the 19th century	underworld organizations