Coptic was an eminent 'language in contact,' mainly borrowing from two donor languages, Greek and Arabic. Greek was spoken and heard in Egypt as early as in the 7th century BCE, a millennium before the standardization of Coptic. Greek merchants who settled in Egypt and Greek mercenaries in the Pharaohs' armies were early agents of linguistic interaction. As a result of the campaigns of Alexander the Great, Greek spread over the Eastern Mediterranean and became the most important lingua franca in the Middle East. In Egypt, where one of Alexander's generals established a Hellenistic dynasty, Greek was used alongside the native Egyptian language from the 4th century BCE up to the 8th century CE. For over 1000 years, Greek functioned both as the spoken language of a courtly, administrative, and urban élite, and as a written language. It gradually dominated administration, economy, literature, sciences, and even private day-to-day correspondence (Ray 2007, Torallas Tovar Sofia 2010, van Minnen 1998, Vierros 2008 & 2012). Only after the conquest of Egypt by the Arabs in the mid-7th century CE did the importance of Greek diminish (Richter 2010). Some of its functional domains became occupied by the Coptic native language, others by Arabic, the language of the new governors. The massive Greek impact on the contemporary Egyptian idiom becomes obvious in thousands of Greek loanwords in Coptic, representing almost all parts of speech and semantic fields (Kasser 1991b, Lefort 1934, Oréal 1999, Rahlf 1912, Reintges 2001 & 2004). The occasional occurrence of Arabic loanwords in 8th- and 9th-century CE Coptic texts indicates incipient Coptic-Arabic contact. Some Coptic texts from the 10th and 11th centuries, the period in which major parts of the indigenous population of Egypt began to shift from their native language to Arabic (Delattre et al. 2012, Papaconstantinou 2007, Zaborowski 2008), bear evidence of intensified borrowing from Arabic (Richter 2006 & 2009).
All in all, it is no exaggeration to say that the Greek-Egyptian contact is the most broadly attested case of language contact in antiquity. Starting with borrowing from Greek into pre-Coptic Egyptian (Clarysse 1987, Fewster 2002, Rutherford 2010), and taking into account borrowing from Arabic to later Coptic, the Egyptian-Coptic language grants us the opportunity to look over 1.500 years of contact-induced language change in a single ancient language under fairly well-known historical and sociolinguistic conditions.
The exceptional wealth of the language data, together with their internal diversity and their diachronic extension, should make investigation into linguistic borrowing into Coptic an important and most rewarding work. However, not at least due to the sheer abundance of data, traditional lexicographical approaches to the loan vocabulary of Coptic (Böhlig 1956, Weiß 1969, Tubach 1999) failed three times during the 20th century.