shell collecting vs aggregation

shell collecting and aggregation both are nouns.

Word	Noun	Adjective	Verb	Adverb
shell collecting	Yes	No	No	No
aggregation	Yes	No	No	No

As nouns, aggregation is a hypernym of shell collecting; that is, aggregation is a word with a broader meaning than shell collecting:

Other hypernyms of shell collecting include assembling, collecting, collection, malacology.

shell collecting (noun)	aggregation (noun)
the collection and study of mollusc shells	the act of gathering something together
	several things grouped together or considered as a whole