costermonger vs trader

costermonger and trader both are nouns.

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

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

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

Other hypernyms of costermonger include bargainer, dealer, monger.

costermonger (noun)	trader (noun)
a hawker of fruit and vegetables from a barrow	someone who purchases and maintains an inventory of goods to be sold