dealer vs truck dealer

dealer and truck dealer both are nouns.

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

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

Other hyponyms of dealer include car dealer, computer dealer, jewelry dealer, jewelry store.

dealer (noun)	truck dealer (noun)
a firm engaged in trading	a firm that sells and buys trucks
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