Hastings' Dictionary of the New Testament 
In dealing with ancient literature we have become accustomed to make a distinction between the epistle and the letter . In that sphere we frequently meet with a so-called letter, which, from the purely external point of view, shows all the characteristics of a genuine letter, and yet is in no sense designed to serve as a vehicle of tidings and ideas between one person and another, or between one person and a definite circle of persons, but on the contrary has been written in the expectation, and indeed with the intention, of gaining the notice of the public. Now, in designating such a document an ‘epistle,’ and reserving the term ‘letter’ for a letter in the true sense, we must remember that, while the distinction itself was quite familiar to the ancients, our terminology is modern. By ‘epistle’ we mean, accordingly, a letter expressly intended for the general public. Yet it must be admitted that, in the sphere of ancient literature, it is not always easy to decide whether a particular document is a letter or an epistle, as will appear from the following considerations. (1) In many such compositions there is nothing to indicate whether the writer desired to address the general public or not. (2) The art of the epistle-writer consisted very largely in his ability to personate a true letter-writer, so that the reader should never have the faintest suspicion that the writing in his hands was anything but a genuine letter. (3) Even in letters properly so called the writer did not always allow his words and thoughts to flow freely and spontaneously, but sometimes-and especially in the latter part of the ancient era, when rhetoric prevailed everywhere-as we find even in correspondence whose private and confidential nature is beyond doubt, invested the structure and style of his letter with rhetorical features such as we might expect to meet with in writings designed to influence the public mind, and therefore of necessity far removed from the free and easy prattle of a letter. (4) Finally, it is not easy to specify the point of transition between the limited circle to which the private letter may be addressed and the general public to which the epistle makes its appeal. In most cases, no doubt, it is possible to decide whether an epistle is meant for the public eye, but it is frequently far from certain whether a particular letter addressed to a limited public, as e.g. a church or a group of churches, or, say, the bishops of a metropolitan province, has not lost all claim to be regarded as a real letter. Notwithstanding these considerations, however, the distinction between epistle and true letter has every right to be retained. Like all such distinctions, it doubtless fails to make due allowance for the living current of literary development, but it teaches us to keep an open eye for the diversities and gradations of literature, and thus also, when rightly used, helps us to define more accurately the character of the epistolary writings in the NT.
Now, as the Christian writers of the Apostolic Age adopted the ‘epistle,’ and, we may even say, made use of it with a zest that may be inferred, in particular, from the fact that they enriched the literary side of the Gospel and the Apocalypse by means of the epistolary form (cf. Luke 1:1 ff., Revelation 1:4 ff.), it is necessary to give due weight to the following points: (1) that in this as in other respects the Apostolic Age was embedded in the same literary tradition of later antiquity as we are able to trace in various Greek and Latin prototypes of non-Christian origin; (2) that, nevertheless, the structure, style, and diction of the primitive Christian epistles nearly always carry us into a different sphere of culture from that. associated with the extant post-classical epistolary literature composed on classical models; and, finally, (3) that the influence of the hortatory addresses of Christian preachers in the primitive Church is clearly traceable in these Christian epistles.
Among the ‘epistles’ of the Apostolic Age the present writer would include the following: James, 1 Peter, Jude, Hebrews, 1 John, and Barnabas. These for the most part differ in no essential point from hortative addresses to a congregation, and the epistolary form, where it is present at all, or where, as in Hebrews, it is no more than suggested, is merely a form, which, in fact, is completely shattered by the contents. Among these Epistles there is not one which in virtue of a refined or even well-schooled art could claim to be considered a true letter. But this is itself a striking evidence of the significant fact that the Christian writers of the Apostolic Age, greatly as they had been affected by the stream of literary activity in the grander style of the ancients, were now feeling their way towards new forms in which to communicate their religious ideas to a wider public. With this end in view, therefore, they had recourse to the epistle, as the literary eidos at once of the simplest character and lying closest to their hands; but here-even in the case of a writer like the author of Hebrews, who has obviously been powerfully influenced by the elements of Greek rhetoric-the substance of the message was for them of much greater importance than the form. The fictitious, pseudonymous epistle is a literary phenomenon that first makes its appearance in the post-Apostolic Age.
Literature.-R. Hercher, Epistolographi Grœci , Paris, 1873 (a collection of Greek letters); H. Peter, Der Brief in der römischen Litteratur , Leipzig, 1901; E. Norden, Die antike Kunstprosa 2, do. 1909; G. A. Deissmann, Bibelstudien , Marburg, 1895, pp. 187-225 (Eng. translation, 1901, pp. 1-59); C. F. G. Heinrici, Der litterarische Character der neutest. Schriften , Leipzig, 1908, p. 56ff.; J. Weiss, ‘Literaturgesch. des NT,’ in RGG [Note: GG Religion in Geschichte und Gegenwart.]iii.  2175-2215; H. Jordan, Gesch. der altchristlichen Literatur , Leipzig, 1911, p. 123ff. (containing also a history of the Christian Epistle till a.d. 600); P. Wendland, Die hellenistischrömische Kultur in ihren Beziehungen zu Judentum und Christentum , ‘Die urchristliche Literaturformen,’ Tübingen, 1912, pp. 342-381.
Fausset's Bible Dictionary 
The first mentioned in the Old Testament is that of David to Joab, sent by Uriah ( 2 Samuel 11:14); a usage perhaps borrowed from the Phoenicians, with whose king Hiram he was intimate. The king's seal was usually attached in token of authority, and to guard against anyone but the person addressed reading it ( 1 Kings 21:8-9). The seal was of clay impressed while moist ( 1 Kings 21:8-9; Job 38:14). "A writing came to Jehoram from Elijah" ( 2 Chronicles 21:12). Originally messages were sent orally ( Genesis 32:3; Numbers 22:5; Numbers 22:7; Numbers 22:16; Numbers 24:12; Judges 11:12-13; 1 Samuel 11:7; 1 Samuel 11:9). Hezekiah had a system of couriers or posts to transmit his letters in various quarters; the plan especially prevalent in Persia ( 2 Chronicles 30:6; 2 Chronicles 30:10; Esther 8:10; Esther 8:14).
We read of his "spreading before the Lord" Sennacherib's letter ( 2 Kings 19:14). Sanballat's "open letter" was an infraction of the etiquette of the Persian court ( Nehemiah 6:5). Jeremiah wrote to the captives in Babylon ( Jeremiah 29:1-3). In the New Testament Luke begins both his "Gospel" and "Acts" in the form of a letter to Theophilus; but in substance both books are rather histories than epistles. Our Lord wrote no epistle, as that to Abgarus king of Edessa is most probably not authentic (Eusebius H. E., 1:13). His office was to enact the facts, and to fulfill the personal ministry, upon which the church was to be founded. The epistles are the inspired commentaries unfolding the truths in the histories, the Gospels, and Acts; just as the prophets interpret the spiritual lessons designed by God to be drawn from the Old Testament histories.
Twenty-one of the 27 New Testament books are strictly epistles. Three more are so in form: Luke, Acts, and Revelation addressed to the seven churches. Matthew, Mark, and John alone are not epistolary either in form or substance. Fourteen, including Hebrew, are by Paul; three by John; two by Peter; one by James; one by Jude. Paul dictated his to an amanuensis, authenticating them with his autograph at the close, wherewith be wrote the salutation "grace be with thee," or "the grace of our Lord Jesus Christ," etc. But, in order to show his regard to the Galatians, whom Judaizers tried to estrange, he wrote all that epistle himself in large characters, for so Galatians 6:11-12 ought to be translated, "ye see in how large letters I have written." The largeness of letters was probably owing to his weakness of sight ( Galatians 4:15).
The words "I have written" ("wrote," Egrapsa ) distinguished this epistle as written by himself from 2 Thessalonians 3:17, "I write," where he only writes the closing salutation. Philemon 1:19 shows that that epistle also was all written by Paul as a special compliment to Philemon; whereas the accompanying epistle to the Colossians ( Colossians 4:18) has only "the salutation" so written, as also 1 Corinthians 16:21. In Romans 16:22 his amanuensis, Tertius, salutes in his own name. Peter's closing salutation is "peace be with you"; as Paul's is "grace," etc. John after Paul's death takes up his closing benediction, "the grace of our Lord Jesus Christ be with you all," at the end of Revelation.
In the beginning of most of Paul's epistles "grace and peace" are his opening greeting; in the pastoral epistles concerning ministers "mercy" is added, "grace, mercy, and peace" (1 and 2 Timothy and Titus), for ministers of all men most need mercy ( 1 Corinthians 7:25; 2 Corinthians 7:1). All the epistles besides Paul's are called "universal" or "general." This designation holds good in a general and not strict sense; for the 2 and 3 John are addressed to specific persons in form, though in substance they are general. The epistolary form of inspiration gives scope for free expression of personal affection, and conveys divine truth, progressively unfolded to us, as to Christian faith, worship and polity with a freshness, point, and communion of heart with heart, such as could hardly be attained by formal, didactic treatises.
American Tract Society Bible Dictionary 
A letter; but the term is applied particularly to the inspired letters in the New Testament, written by the apostles on various occasions, to approve, condemn, or direct the conduct of Christian churches. The Holy Spirit has thus provided that we should have the great doctrines of the true gospel not only historically stated by the evangelists, but applied familiarly to the various emergencies of daily life. It is not to be supposed that every note or memorandum written by the hands of the apostles, or by their direction, was divinely inspired, or proper for preservation to distant ages. Compare 1 Corinthians 5:9 Colossians 4:16 . Those only have been preserved by the overruling hand of Providence which were so inspired, and from which useful directions had been drawn, and might in after-ages be drawn, as from a perpetual directory, for faith and practice-always supposing that similar circumstances require similar directions. In reading an Epistle, we ought to consider the occasion of it, the circumstances of those to whom it was addressed, the time when written, the general scope and design of it, as well as the intention of particular arguments and passages. We ought also to observe the style and manner of the writer, his mode of expression, the peculiar effect he designed to produce on those to whom he wrote, to whose temper, manners, general principles, and actual situation, he might address his arguments, etc.
Of the books of the New Testament, twenty-one are epistles; fourteen of them by Paul, one by James, two by Peter, three by John, and one by Jude. Being placed in our canon without reference to their chronological order, they are perused under considerable disadvantages; and it would be well to read them occasionally in connection with what the history in the Acts of the Apostles relates respecting the several churches to which they are addressed. This would also give us nearly their order of time, which should also be considered, together with the situation of the writer; as it may naturally be inferred that such compositions would partake of the writer's recent and present feelings. The epistles and James, by Peter and Jude, are very different in their style and application from those of Paul written to the Gentiles; and those of Paul written to the Gentiles; and those of Paul no doubt contain expressions and allude to facts much more familiar to their original readers than to later ages.
Vine's Expository Dictionary of NT Words 
primarily "a message" (from epistello, "to send to"), hence, "a letter, an epistle," is used in the singular, e.g., Acts 15:30; in the plural, e.g., Acts 9:2; 2—Corinthians 10:10 . "Epistle is a less common word for a letter. A letter affords a writer more freedom, both in subject and expression, than does a formal treatise. A letter is usually occasional, that is, it is written in consequence of some circumstance which requires to be dealt with promptly. The style of a letter depends largely on the occasion that calls it forth." * [* From Notes on Thessalonians, by Hogg and Vine, p. 5.] "A broad line is to be drawn between the letter and the epistle. The one is essentially a spontaneous product dominated throughout by the image of the reader, his sympathies and interests, instinct also with the writer's own soul: it is virtually one half of an imaginary dialogue, the suppressed responses of the other party shaping the course of what is actually written ...; the other has a general aim, addressing all and sundry whom it may concern: it is like a public speech and looks towards publication" (J. V. Bartlet, in Hastings' Bib. Dic.)
Webster's Dictionary 
(1): ( n.) A writing directed or sent to a person or persons; a written communication; a letter; - applied usually to formal, didactic, or elegant letters.
(2): ( n.) One of the letters in the New Testament which were addressed to their Christian brethren by Apostles.
(3): ( v. t.) To write; to communicate in a letter or by writing.
King James Dictionary 
EPIS'TLE, n. epis'l. L. epistola Gr. to send to to send.
A writing, directed or sent, communicating intelligence to a distant person a letter a letter missive. It is rarely used in familiar conversation or writings, but chiefly in solemn or formal transactions. It is used particularly in speaking of the letters of the Apostles, as the epistles of Paul and of other letters written by the ancients, as the epistles of Pliny or of Cicero.
International Standard Bible Encyclopedia 
ē̇ - pis ´' l ( ἐπιστολή , epistolḗ , "a letter," "epistle"; from ἐπιστέλλω , epistéllō , "to send to"):
1. New Testament Epistles
2. Distinctive Characteristics
3. Letter-Writing in Antiquity
4. Letters in the Old Testament
5. Letters in the Apocrypha
6. Epistolary Writings in the New Testament
7. Epistles as Distinguished from Letters
8. Patristic Epistles
9. Apocryphal Epistles
1. New Testament Epistles
A written communication; a term inclusive of all forms of written correspondence, personal and official, in vogue from an early antiquity. As applied to the twenty-one letters, which constitute well-nigh one-half of the New Testament, the word "epistle" has come to have chiefly a technical and exclusive meaning. It refers, in common usage, to the communications addressed by five (possibly six) New Testament writers to individual or collective churches, or to single persons or groups of Christian disciples. Thirteen of these letters were written by Paul; three by John; two by Peter; one each by James and Jude; one - the epistle to the Hebrews - by an unknown writer.
2. Distinctive Characteristics
As a whole the Epistles are classified as Pauline, and Catholic, i.e. general; the Pauline being divided into two classes: those written to churches and to individuals, the latter being known as Pastoral (1 and 2 Timothy, and Titus; some also including Philemon; see Lange on Romans , American edition, 16). The fact that the New Testament is so largely composed of letters distinguishes it, most uniquely, from all the sacred writings of the world. The Scriptures of other oriental religions - the Vedas, the Zend Avesta, the Tripitaka, the Koran, the writings of Confucius - lack the direct and personal address altogether. The Epistles of the New Testament are specifically the product of a new spiritual life and era. They deal, not with truth in the abstract, but in the concrete. They have to do with the soul's inner experiences and processes. They are the burning and heart-throbbing messages of the apostles and their confreres to the fellow-Christians of their own day. The chosen disciples who witnessed the events following the resurrection of Jesus and received the power ( Acts 1:8 ) bestowed by the Holy Spirit on, and subsequent to, the Day of Pentecost, were spiritually a new order of men. The only approach to them in the spiritual history of mankind is the ancient Hebrew prophets. Consequently the Epistles, penned by men who had experienced a great redemption and the marvelous intellectual emancipation and quickening that came with it, were an altogether new type of literature. Their object is personal. They relate the vital truths of the resurrection era, and the fundamental principles of the new teaching, to the individual and collective life of all believers. This specific aim accounts for the form in which the apostolic letters were written. The logic of this practical aim appears conspicuously in the orderly Epistles of Paul who, after the opening salutation in each letter, lays down with marvelous clearness the doctrinal basis on which he builds the practical duties of daily Christian life. Following these, as each case may require, are the personal messages and affectionate greetings and directions, suited to this familiar form of address.
The Epistles consequently have a charm, a directness, a vitality and power unknown to the other sacred writings of the world. Nowhere are they equaled or surpassed except in the personal instructions that fell from the lips of Jesus. Devoted exclusively to experimental and practical religion they have, with the teachings of Christ, become the textbook of the spiritual life for the Christian church in all subsequent time. For this reason "they are of more real value to the church than all the systems of theology, from Origen to Schleiermacher" (Schaff on St.Paul's Epistles, History of the Christian Church , 741). No writings in history so unfold the nature and processes of the redemptive experience. In Paul and John, especially, the pastoral instinct is ever supreme. Their letters are too human, too personal, too vital to be formal treatises or arguments. They throb with passion for truth and love for souls. Their directness and affectionate intensity convert their authors into prophets of truth, preachers of grace, lovers of men and missionaries of the cross. Hence, their value as spiritual biographies of the writers is immeasurable. As letters are the most spontaneous and the freest form of writing, the New Testament Epistles are the very life-blood of Christianity. They present theology, doctrine, truth, appeal, in terms of life, and pulsate with a vitality that will be fresh and re-creative till the end of time. (For detailed study of their chronology, contents and distinguishing characteristics, see articles on the separate epistles.)
3. Letter-Writing in Antiquity
While the New Testament Epistles, in style and quality, are distinct from and superior to all other literature of this class, they nevertheless belong to a form of personal and written address common to all ages. The earliest known writings were epistolary, unless we except some of the chronologies and inscriptions of the ancient Babylonian and Assyrian kings. Some of these royal inscriptions carry the art of writing back to 3800 bc, possibly to a period still earlier (see Goodspeed, Kent's Historical Series , 42-43, secs. 40-41), and excavations have brought to light "an immense mass of letters from officials to the court - correspondence between royal personages or between minor officials," as early as the reign of K H̬ammurabi of Babylon, about 2275 bc (ibid., 33). The civilized world was astonished at the extent of this international correspondence as revealed in the Tell el-Amarna Letters (1480 bc), discovered in Egypt in 1887, among the ruins of the palace of Amenophis IV. This mass of political correspondence is thus approximately synchronous with the Hebrew exodus and the invasion of Canaan under Joshua.
4. Letters in the Old Testament
As might be expected, then, the Old Testament abounds with evidences of extensive epistolary correspondence in and between the oriental nations. That a postal service was in existence in the time of Job ( Job 9:25 ) is evident from the Hebrew term רצים , rācı̄m , signifying "runners," and used of the mounted couriers of the Persians who carried the royal edicts to the provinces. The most striking illustration of this courier service in the Old Testament occurs in Esther 3:13 , Esther 3:15; Esther 8:10 , Esther 8:14 where King Ahasuerus , in the days of Queen Esther, twice sends royal letters to the Jews and satraps of his entire realm from India to Ethiopia, on the swiftest horses. According to Herodotus, these were usually stationed, for the sake of the greatest speed, four parasangs apart. Hezekiah's letters to Ephraim and Manasseh were sent in the same way ( 2 Chronicles 30:1 , 2 Chronicles 30:6 , 2 Chronicles 30:10 ). Other instances of epistolary messages or communications in the Old Testament are David's letter to Joab concerning Uriah and sent by him ( 2 Samuel 11:14 , 2 Samuel 11:15 ); Jezebel's, to the elders and nobles of Jezreel, sent in Ahab's name, regarding Naboth ( 1 Kings 21:8 , 1 Kings 21:9 ); the letter of Ben-hadad, king of Syria, to Jehoram, king of Israel, by the hand of Naaman ( 2 Kings 5:5-7 ); Jehu's letters to the rulers of Jezreel, in Samaria ( 2 Kings 10:1 , 2 Kings 10:2 , 2 Kings 10:6 , 2 Kings 10:7 ); Sennacherib's letter to Hezekiah ( 2 Kings 19:14; Isaiah 37:14; 2 Chronicles 32:17 ), and also that of Merodach-baladan, accompanied with a gift ( 2 Kings 20:12; Isaiah 39:1 ). Approximating the New Testament epistle in purpose and spirit is the letter of earnest and loving counsel sent by Jeremiah to the exiles in Babylon. It is both apostolic and pastoral in its prophetic fervor, and is recorded in full ( Jeremiah 29:1 , 4-32) with its reference to the bitterly hostile and jealous letter of Shemaiah, the false prophet, in reply.
As many writers have well indicated, the Babylonian captivity must have been a great stimulus to letter-writing on the part of the separated Hebrews, and between the far East and Palestine. Evidences of this appear in the histories of Ezra and Nehemiah, e.g. the correspondence, back and forth, between the enemies of the Jews at Jerusalem and Artaxerxes, king of Persia, written in the Syrian language (Ezr 4:7-23); also the letter of Tattenai (the King James Version "Tatnai") the governor to King Darius ( Ezra 5:6-17 ); that of Artaxerxes to Ezra ( Ezra 7:11 ), and to Asaph, keeper of the royal forest ( Nehemiah 2:8 ); finally the interchange of letters between the nobles of Judah and Tobiah; and those of the latter to Nehemiah ( Nehemiah 6:17 , Nehemiah 6:19; so Sanballat Nehemiah 6:5 ).
5. Letters in the Apocrypha
The Old Testament Apocrypha contains choice specimens of personal and official letters, approximating in literary form the epistles of the New Testament. In each case they begin, like the latter, in true epistolary form with a salutation: "greeting" or "sendeth greeting" (1 Macc 11:30, 32; 12:6, 20; 15:2, 16), and in two instances closing with the customary "Fare ye well" or "Farewell" (2 Macc 11:27-33, 34-38; compare 2 Corinthians 13:11 ), so universally characteristic of letter-writing in the Hellenistic era.
6. Epistolary Writings in the New Testament
The most felicitous and perfect example official correspondence in the New Testament is Claudius Lysias' letter to Felix regarding Paul ( Acts 23:25-30 ). Equally complete in form is the letter, sent, evidently in duplicate, by the apostles and elders to their Gentile brethren in the provinces of Asia ( Acts 15:23-29 ). In these two letters we have the first, and with James 1:1 , the only, instance of the Greek form of salutation in the New Testament (χαίρειν , chaı́rein ). The latter is by many scholars regarded as probably the oldest letter in epistolary form in the New Testament, being in purport and substance a Pastoral Letter issued by the Apostolic Council of Jerusalem to the churches of Antioch, Syria and Cilicia. It contained instructions as to the basis of Christian fellowship, similar to those of the great apostle to the churches under his care.
The letters of the high priest at Jerusalem commending Saul of Tarsus to the synagogues of Damascus are samples of the customary letters of introduction ( Acts 9:2; Acts 22:5; compare Acts 28:21; also Acts 18:27 ). As a Christian apostle Paul refers to this common use of "epistles of commendation" ( 2 Corinthians 3:1; 1 Corinthians 16:3 ) and himself made happy use of the same ( Romans 16:1 ); he also mentions receiving letters, in turn, from the churches ( 1 Corinthians 7:1 ).
Worthy of classification as veritable epistles are the letters, under the special guidance of the Holy Spirit, to the seven churches of Asia (Rev 2:1 through 3:22). In fact, the entire Book of Rev is markedly epistolary in form, beginning with the benedictory salutation of personal and apostolic address, and closing with the benediction common to the Pauline epistles. This again distinguishes the New Testament literature in spirit and form from all other sacred writings, being almost exclusively direct and personal, whether in vocal or written address. In this respect the gospels, histories and epistles are alike the product and exponent of a new spiritual era in the life of mankind.
7. Epistles as Distinguished from Letters
This survey of epistolary writing in the far East, and especially in the Old Testament and New Testament periods, is not intended to obscure the distinction between the letter and the epistle . A clear line of demarcation separates them, owing not merely to differences in form and substance, but to the exalted spiritual mission and character of the apostolic letters. The characterization of a letter as more distinctly personal, confidential and spontaneous, and the epistle as more general in aim and more suited to or intended for publication, accounts only in part for the classification. Even when addressed to churches Paul's epistles were as spontaneous and intimately and affectionately personal as the ordinary correspondence. While intended for general circulation it is doubtful if any of the epistolary writers of the New Testament ever anticipated such extensive and permanent use of their letters as is made possible in the modern world of printing. The epistles of the New Testament are lifted into a distinct category by their spiritual eminence and power, and have given the word epistle a meaning and quality that will forever distinguish it from letter . In this distinction appears that Divine element usually defined as inspiration: a vitality and spiritual endowment which keeps the writings of the apostles permanently "living and powerful," where those of their successors pass into disuse and obscurity.
8. Patristic Epistles
Such was the influence of the New Testament Epistles on the literature of early Christianity that the patristic and pseudepigraphic writings of the next century assumed chiefly the epistolary form. In letters to churches and individuals the apostolic Fathers, as far as possible, reproduced their spirit, quality and style. See Literature , Sub-Apostolic .
9. Apocryphal Epistles
Pseudo-epistles extensively appeared after the patristic era, many of them written and circulated in the name of the apostles and apostolic Fathers. See Apocryphal Epistles . This early tendency to hide ambitious or possibly heretical writings under apostolic authority and Scriptural guise may have accounted for the anathema pronounced by John against all who should attempt to add to or detract from the inspired revelation ( Revelation 22:18 , Revelation 22:19 ). It is hardly to be supposed that all the apostolic letters and writings have escaped destruction. Paul in his epistles refers a number of times to letters of his that do not now exist and that evidently were written quite frequently to the churches under his care ( 1 Corinthians 5:9; 2 Corinthians 10:9 , 2 Corinthians 10:10; Ephesians 3:3 ); "in every epistle" ( 2 Thessalonians 3:17 ) indicates not merely the apostle's uniform method of subscription but an extensive correspondence. Colossians 4:16 speaks of an "epistle from Laodicea," now lost, doubtless written by Paul himself to the church at Laodicea, and to be returned by it in exchange for his epistle to the church at Colosse.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
In the Acts of the Apostles we have the short epistle addressed by the apostolic council held at Jerusalem to the Gentile converts in Antioch, Syria, and Cilicia ( Acts 15:23-24). There is also a letter from Claudius Lysias to Felix, which may be supposed to preserve the official style of the provinces. Both these use the common Greek formulas, beginning, after the names of the writer and the person written to, with the salutation, and ending with the adieu. The epistles of the N.T. in their outward form are such as might be expected from men who were brought into contact with Greek and Roman customs, themselves belonging to a different race, and so reproducing the imported style with only partial accuracy. They begin (the Epistle to the Hebrews and 1 John excepted) with the names of the writer, and those to whom the epistle is addressed. Then follows the formula of salutation (analogous to the Ε῏Υ Πράττειν of Greek, the ''S.,'' S. ''D'' or S.D.M., Salutem, Salutem Dicit, Salutem Dicit Multam, of Latin correspondence) — generally in Paul's Epistles in some combination of the words "grace, mercy, and peace" ( Χάρις , Ἔλεος , Εἰρήνη ); in others, as in Acts 15:23; James 1:1, with the closer equivalent of Χαίρειν , "greeting," which last is never used by Paul. Then the letter itself commences in the first person, the singular and plural being used, as in the letters of Cicero, indiscriminately (comp. 1 Corinthians 2:1-16; 2 Corinthians 1:8; 2 Corinthians 1:15; 1 Thessalonians 3:1-2; and passim). When the substance of the letter has been completed, questions answered, truths enforced, there come the individual messages, characteristic, in Paul's Epistles especially, of one who never allowed his personal affections to be swallowed up in the greatness of his work. The conclusion in this case was probably modified by the fact that the letters were dictated to an amanuensis. When he had done his work, the apostle took up the pen o - reed, and added, in his own large characters ( Galatians 6:11), the authenticating autograph, sometimes with special stress on the fact that this was his writing ( 1 Corinthians 16:21; Galatians 6:11; Colossians 4:18; 2 Thessalonians 3:17), always with one of the closing formula of salutation, "Grace be with thee" — "the grace of our Lord Jesus Christ be with your spirit." In one instance, Romans 16:22, the amanuensis in his own name adds his salutation. In the "farewell" ( Ἔῤῥωσο of Acts 23:30, Ἔῤῥωσθε of Acts 15:29) we have the equivalents to the Vale, Valete, which formed the custonary conclusion of Roman letters. It need hardly be said that the fact that Paul's Epistles were dictated in this way accounts for many of their most striking peculiarities, the frequent digressions, the long parentheses, the vehemence and energy as of a man who is speaking strongly as his feelings prompt him rather than writing calmly. An allusion in 2 Corinthians 3:1 brings before us another class of letters which must have been in frequent use in the early ages of the Christian Church, the Ἐπιστολαί Συστατικαί , or Letters Of Recommendation, by which travelers or teachers were commended by one church to the good offices of others. Other persons (there May Be a reference to Apollos, Copyright StatementThese files are public domain. Bibliography InformationMcClintock, John. Strong, James. Entry for 'Epistle'. Cyclopedia of Biblical, Theological and Ecclesiastical Literature. https://www.studylight.org/encyclopedias/eng/tce/e/epistle.html. Harper & Brothers. New York. 1870.
- Epistle from Hastings' Dictionary of the New Testament
- Epistle from Fausset's Bible Dictionary
- Epistle from American Tract Society Bible Dictionary
- Epistle from Vine's Expository Dictionary of NT Words
- Epistle from Webster's Dictionary
- Epistle from King James Dictionary
- Epistle from International Standard Bible Encyclopedia
- Epistle from Cyclopedia of Biblical, Theological and Ecclesiastical Literature