retailing vs merchandising

retailing and merchandising both are nouns.

Word	Noun	Adjective	Verb	Adverb
retailing	Yes	No	No	No
merchandising	Yes	No	No	No

As nouns, merchandising is a hypernym of retailing; that is, merchandising is a word with a broader meaning than retailing:

retailing: the activities involved in selling commodities directly to consumers
merchandising: the exchange of goods for an agreed sum of money

Other hypernyms of retailing include marketing, selling.

retailing (noun)	merchandising (noun)
the activities involved in selling commodities directly to consumers	the exchange of goods for an agreed sum of money
	the business of drawing public attention to goods and services
	branded products meant to promote another product, especially films and pop groups