It is important to note here that the Greeks learned their writing system from the Egyptians through the frequent travelers of the ancient world, the Phoenicians. In the course of their commercial dealings with the Egyptians, the Phoenicians imported the Egyptian script and molded it into an alphabet with a far smaller number of characters, all pronounceable and all consonants. As they traveled the Mediterranean and traded with the inhabitants of the Greek Isles, they gave their version of the Egyptian writing system to the Greeks. They in turn revised its orthography and added a number of written vowels. A system that eventually became the basis for the new Egyptian script, i.e. the Coptic.
The pagan Egyptian priests, as a result of the invasion of the Greek language, found themselves at a disadvantage. The source of income as well as the power of their temples depended a great deal on the making and the sales of magical amulets. Now these amulets, written in Egyptian, can not be pronounced by those who can afford to pay for them. If they can not use, properly or at all, it is safe to say that they would not buy it. To avert such economic and religious massacre, they reverted to a transliteration system of these amulets. This new system used the Greek characters along with several other characters borrowed from the Demotic to denote sounds not available in Greek. The economic success of such system made them extend its use to other applications such as horoscopes and the like. The number of borrowed Demotic characters eventually were reduced. The resultant script was highly standardized, in the common tradition of the Ancient Egyptians.
The first visible signs of such presence were rather blemishing to the character of the Church. Two teachers of Gnostic, heterodox repute, traveled abroad at different times during the middle of the second century AD. They were Basilides and Valentinus. The latter became infamous due to his quest to be the bishop of Rome. In any case, these teachers influenced the arrival of Pantanus, the missionary, presumably to introduce the orthodox teachings of Christianity to a seemingly Gnostic community. After his arrival he discovered that this was not exactly the case and there was a strong orthodox community present as a result of the evangelizing work of St. Mark and his successors. Being a renowned Christian teacher he was put in charge of the Christian school of Alexandria, a rather small school that taught those who are willing to serve the Lord the fundamentals of Christianity. Shortly after his arrival, St. Demetrius, the first bishop of Egyptian origin, became the bishop of Alexandria about 189 AD.
The contact between Pantaenus, the missionary, and St. Demetrius the representative of the large and mostly non-Christian Egyptians was truly a match made in Heaven. As a result a missionary movement to convert the Egyptian peasants began. The School of Alexandria probably became a school to prepare the missionaries and direct their activities.
The dilemma faced by those responsible for directing such missionary work was the uniformity of the message to be given to the Egyptians. The missionaries knew how to read Greek but not Demotic. The Egyptian peasants did not know how to read either but they understood the sounds of the language written by the Demotic script, i.e. Egyptian. To insure that the Word of God, written in the Scriptures, be preached the same by the different missionaries, it had to be written in a way that the missionaries can read and the Egyptians can understood when it was read to them. So the missionaries translated the Scriptures into the Egyptian tongue but wrote them using the Greek characters they are familiar with. These attempts differed from those of the pagans in that they did not use any Demotic character in the beginning. The shortcomings of that system were eventually realized and more characters, borrowed from the Demotic, were added to bring them to the current six or seven additional characters that survived in the Sahidic and Bohairic dialects respectively.
All the dialects were to a large extent geographically-dependent. Their spanned the entire length of the Nile Valley. Based on literary records we have such dialects as the Akhmimic and the Lycopolitan (Asyutic) dialects of Upper Egypt, the Middle Egyptian and the Fayoumic of Middle Egypt, and the Bohairic of the Delta. Then there is the Sahidic dialect that became, from the earliest times, a neutral dialect used throughout Egypt and eventually gained literary dominance with the extensive writings of St. Shenouda the Archimandrite. There is also a host of minor dialects as well as subdialects to the ones mentioned above.
Now Bohairic is the only surviving dialect of Coptic. It was kept alive first by the strength of the monastic communities of Wadi n' Natrun which used it extensively. Then with the move of the Patriarchate from Alexandria to Cairo in the 11th century, Bohairic, the dialect of the District, became the official dialect of the Church replacing the Sahidic.
So with monastic fathers like St. Antony, St. Pachomius, and St. Macarius and their respective disciples writing to their monks; and Church Fathers like St. Athanasius, St. Theophilius, and St. Cyril writing also to them in Coptic, the Golden Age of Coptic was about to begin.
It was not until St. Shenouda the Archimandrite came on the scene that Coptic really achieved its literary excellence. St. Shenouda who lived from 348 to 466 AD. was able to transform the language form a tool to communicate instructions to the monks to a wide-variety literary language that addressed monks, ecclesiastic authorities, laymen, and even government officials. His charisma, knowledge of Greek language and rhetoric, and his innovative mind gave him the necessary tools to elevate the Coptic language, in content and style, to a literary height never achieved before nor equaled since. The Coptic scholars are constantly astounded by his great writings as more and more of them are being studied and accurately published.
This literary legacy continued to a lesser degree through the writings of his disciple St. Besa in the second half of the fifth century. But such writings were mostly for the edification of the large monastic community in the White Monastery. later in the sixth and seventh centuries other fathers wrote many works in Coptic like Rufus of Shotep, Constantine of Asyut, and Pisentius of Qift.
Ecclesiastically, the language continued strong. In fact, a great number of Hagiographic texts were composed during the early parts of this period. Coptic continued to be used in the Church with Greek as the second language, as seen from the texts that survived from the period. However a relatively small number of liturgical manuscripts survived from such period to show how it was being used. This was due to the heavy use that such manuscripts were subjected to, poor preservation during the period of decline in use, and the parchment material they were written on that did not lend itself to such heavy use.
During this period some Arabic loan-words made their way into the language. But there was no indication that the Arabic language was used in the Church. There were no Coptic-Arabic manuscripts that belong to this period or any literary citation to indicate its possible use. Coptic was also the spoken language of the peasants and probably the clergy.
During the same period, the European Crusaders waged their wars against the Moslem rulers of the Middle East in an effort to secure the holy places. Their presence in the area generated waves of persecutions and oppressions against the Copts. This was due to the Moslems seeing in the sign of the Cross, displayed by the Crusaders, an implied alliance of the Copts with those invaders and a great threat to the country. Of course there was no chance of such alliance, for the Crusaders considered the Copts as heretics and treated them worse than they treated the Moslems, as sad as it might sounds. Introduction of Arabic in the 12th century by Patriarch Gabriel ibn Turaik was probably an attempt to show the Moslems that the Copts are different from real enemy that they were fighting.
Such move may have been considered wise at the time but it actually opened the flood gates. Christians Arabic literature flourished afterward. Later in the period, Arabic invaded the liturgical books, replacing Greek in bilingual texts and intruding on traditionally non-bilingual ones. Even purely Arabic liturgical texts began to appear, indicating that Arabic moved from a mere reference translation to actual use in the churches. Original composition in Coptic became limited to liturgical hymns and prayers. The only Coptic literary texts composed in the later part of the period were the martyrdom of St. John of Phanidijoit, written as such to shield from the eyes of the Moslems, and compositions, urging the Copts to revive their language.
Further testimony to the gradual decline of the language as a reading tool was supplied by the many lexicographic works that were introduced during the period. They were in the form of Muqadimat (Grammar) and Salalem (Scalae or word lists). Another sign of decline was Arabic texts circulating among the monks but written in Coptic characters, as they could not still read the Arabic script. This eventually was replaced with the writing of Coptic text in Arabic letters that we see nowadays in the Coptic Church.
In summary, this period saw the decline of Coptic literary use in its last stronghold, the Church. Eventually, it led to the weakening of the Church which subsequently weakened the language more, a natural chain reaction. The number of Christians declined due to conversion to Islam. This can probably be attributed to the decline in Coptic which represented a cultural barrier for the Copts from the Arabic-Moslem Culture. But now the increasing use of Arabic bridged that barrier and made it easier for the border-line Christians to cross to seemingly greener grounds!
St. Cyril did not last long on the throne of St. Mark. In fact too short of time for such a great figure in Church history. His death was in part brought upon by opponents of his reforms. But he laid the ground work for such movement to continue. In the last half quarter of that century the movement to revive the Coptic language intensified. The eyes of those in that movement turned to Greece in an effort to establish a standardized method of pronouncing Coptic. It was felt that Greek preserved the original sound value of many of the characters in Coptic because of its close association with Coptic in its early days. However the Greek tongue underwent some modifications due to the effect of 150 years of Turkish (Ottoman) dominance. Because of the lack of any other available means, a new pronunciation system was established for Coptic that made it sounds not as Egyptian as it should have sounded.
In spite of the above shortcoming, those dedicated people spread the language among the masses. They printed many of the Coptic service books for the first time, as they were only extant in manuscript form. Thus reviving the use of Coptic in the Church services. Several works of grammar was produced as a result along with a more comprehensive dictionary that was available before. The establishment of the Clerical College also aided in the propagation of the movement.