dealer vs merchandiser

dealer and merchandiser both are nouns.

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

As nouns, merchandiser is a hypernym of dealer; that is, merchandiser is a word with a broader meaning than dealer:

dealer: someone who purchases and maintains an inventory of goods to be sold
merchandiser: a businessperson engaged in retail trade

Other hypernyms of dealer include merchant.

dealer (noun)	merchandiser (noun)
a firm engaged in trading	a businessperson engaged in retail trade
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