stamp collecting vs aggregation

stamp collecting and aggregation both are nouns.

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

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

Other hypernyms of stamp collecting include assembling, collecting, collection.

stamp collecting (noun)	aggregation (noun)
the collection and study of postage stamps	the act of gathering something together
	several things grouped together or considered as a whole