accumulated
v.v. to collect or gather more of something over a long period of time. You use this when things like money, dust, or experience grow slowly into a large amount.
v. to gather or acquire an increasing quantity of something over a period of time. Transitive when referring to the collection of objects or assets; intransitive when describing a natural buildup.
He accumulated a lot of debt during his university years.
Dust had accumulated on the old piano after years of neglect in the attic.
The legal team spent months reviewing the evidence they had accumulated, looking for any small detail that might prove their client's innocence in the upcoming trial.
The verb is often used in the passive voice ('has been accumulated') or as a past participle acting as an adjective ('accumulated wealth').
The snow accumulated itself on the roof.The snow accumulated on the roof.When describing a natural buildup, the verb is intransitive and does not require a reflexive pronoun like 'itself'.