Present participle of cumulate; the ongoing process of gathering together, accumulating, or heaping up progressively.
From Latin 'cumulare' + '-ing' gerund/participle suffix; the progressive form describing the continuous action of accumulation.
Using 'cumulating' instead of 'accumulating' signals you're trying to sound academic or technical—it's the kind of word choice that makes writing feel more formal and scientific, which is exactly when and where it appears.
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