class vs art class

class and art class both are nouns.

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

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

class (noun)	art class (noun)
education imparted in a series of lessons or meetings	a class in which you learn to draw or paint
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)	art class (verb)
arrange or order by classes or categories