dealer vs drug dealer

dealer and drug dealer both are nouns.

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

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

Other hyponyms of dealer include drug peddler, drug trafficker, peddler, pusher.

dealer (noun)	drug dealer (noun)
a firm engaged in trading	an unlicensed dealer in illegal drugs
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