In a manner related to or characteristic of documentary; presenting information as factual records or evidence.
From documentary plus the suffix -ily (the adverbial form). A rare word used when describing how something is done in a documentary style or based on documents.
This is one of those words so specialized that even word nerds forget it exists—you'd almost never hear it spoken, but archivists and scholars use it to describe an approach that's strictly document-based and evidence-driven.
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