procession vs aggregation

procession and aggregation both are nouns.

Word	Noun	Adjective	Verb	Adverb
procession	Yes	No	No	No
aggregation	Yes	No	No	No

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

procession: the group action of a collection of people or animals or vehicles moving ahead in more or less regular formation
aggregation: several things grouped together or considered as a whole

Other hypernyms of procession include group action, accumulation, assemblage, collection.

procession (noun)	aggregation (noun)
the group action of a collection of people or animals or vehicles moving ahead in more or less regular formation	the act of gathering something together
the act of moving forward (as toward a goal)	several things grouped together or considered as a whole
(theology) the origination of the Holy Spirit at Pentecost