underworld vs social class

underworld and social class both are nouns.

Word	Noun	Adjective	Verb	Adverb
underworld	Yes	No	No	No
social class	Yes	No	No	No

As nouns, social class is a hypernym of underworld; that is, social class is a word with a broader meaning than underworld:

underworld: the criminal class
social class: people having the same social, economic, or educational status

Other hypernyms of underworld include class, socio-economic class, stratum.

underworld (noun)	social class (noun)
(religion) the world of the dead	people having the same social, economic, or educational status
the criminal class