lower class vs class

lower class and class both are nouns.

Word	Noun	Adjective	Verb	Adverb
lower class	Yes	No	No	No
class	Yes	No	Yes	No

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

Other hypernyms of lower class include social class, socio-economic class, stratum.

lower class (noun)	class (noun)
the social class lowest in the social hierarchy	education imparted in a series of lessons or meetings
	elegance in dress or behavior
	a collection of things sharing a common attribute
	people having the same social, economic, or educational status
	(biology) a taxonomic group containing one or more orders
	a body of students who are taught together
	a body of students who graduate together
	a league ranked by quality

lower class (verb)	class (verb)
	arrange or order by classes or categories