purchasing vs shopping

purchasing and shopping both are nouns.

Word	Noun	Adjective	Verb	Adverb
purchasing	Yes	No	No	No
shopping	Yes	No	No	No

As nouns, shopping is a hyponym of purchasing; that is, shopping is a word with a more specific, narrower meaning than purchasing:

Other hyponyms of purchasing include catalog buying, mail-order buying, viatication, viaticus.

purchasing (noun)	shopping (noun)
the act of buying	searching for or buying goods or services
	the commodities purchased from stores