trader vs merchandiser

trader and merchandiser both are nouns.

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

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

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

Other hypernyms of trader include merchant.

trader (noun)	merchandiser (noun)
someone who purchases and maintains an inventory of goods to be sold	a businessperson engaged in retail trade