dealer vs art dealer

dealer and art dealer both are nouns.

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

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

dealer: someone who purchases and maintains an inventory of goods to be sold
art dealer: a dealer in works of art requiring esthetic evaluation

dealer (noun)	art dealer (noun)
a firm engaged in trading	a dealer in works of art requiring esthetic evaluation
a seller of illicit goods
the person who distributes the playing cards in a card game
someone who purchases and maintains an inventory of goods to be sold
the major party to a financial transaction at a stock exchange; buys and sells for his own account