Epistle

'An epistle' means 'a letter', in the sense of a written communication or message. It derives from Greek. The word is rarely used in current English except in reference to the letters in the New Testament written by the Apostles to the scattered congregations of Christians. 'The Epistle' is a reading from one of these during, and as part of, a church service.

You may also see the word used for certain verse compositions by, or in imitation of, classical Latin or Greek authors. Otherwise, its use nowadays is nearly always jocular.