epistle

This term carries a weight of formality and solemnity that distinguishes it from a common letter. It suggests a purposeful, instructional, or spiritual intent, often implying that the text is meant to be preserved as a permanent record or read aloud to an audience rather than serving as a private correspondence.

In a religious context, it refers specifically to the New Testament letters, where it functions as a technical term for scripture. In secular usage, the word is often used with a touch of irony or grandiosity to describe an excessively long or overly formal piece of writing.