e·pis·tle / iˈpisəl/ • n. formal a letter. ∎  a poem or other literary work in the form of a letter or series of letters. ∎  (also Epistle) a book of the New Testament in the form of a letter from an Apostle: St. Paul's epistle to the Romans. ∎  an extract from an Epistle (or another New Testament book not a Gospel) that is read in a church service.ORIGIN: Old English, via Latin from Greek epistolē, from epistellein ‘send news,’ from epi ‘upon, in addition’ + stellein ‘send.’ The word was reintroduced in Middle English from Old French.

Epistle in the Christian Church, a book of the New Testament in the form of a letter from an Apostle.

Epistle also denotes an extract from an Epistle (or another New Testament book not a Gospel) that is read in a church service.
Epistle side in a church, the south end of an altar, from which the Epistle is traditionally read (opposite to the north or Gospel side).

epistle apostolic letter of the N. T. XIII; (gen.) letter XIV. OE. epistol, beside pistol, ME. pistle — L. epistola; ME. epistle — OF. epistle (mod. épître) — L. epistola — Gr. epistolḗ, f. epistéllein send, esp. as a message, f. EPI- +stéllein send.
So epistolary XV. f. F. épistolaire or L. epistolāris.

Epistle. The usual word for a letter, especially of the New Testament, and in liturgical use.