costermonger vs dealer

costermonger and dealer both are nouns.

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

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

costermonger: a hawker of fruit and vegetables from a barrow
dealer: someone who purchases and maintains an inventory of goods to be sold

Other hypernyms of costermonger include bargainer, monger, trader.

costermonger (noun)	dealer (noun)
a hawker of fruit and vegetables from a barrow	a firm engaged in trading
	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