class vs lower class

class and lower class both are nouns.

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

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

class (noun)	lower class (noun)
education imparted in a series of lessons or meetings	the social class lowest in the social hierarchy
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

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