Jesus was born in “the fullness of time” (Gal 4:4), in a world dominated by Greek culture and Roman governance. Several propitious states of affairs providentially came together at this time, making it the perfect time for the Messiah to come—and also for the church to begin. One important aspect of the first century AD world is that the gospel message could be spread quickly after the formation of the church because the whole Mediterranean world shared a common government—allowing for freedom of travel—and also because the world understood a common language, which was called Koine Greek. Were it not for this common language, the books of the New Testament probably would have been written in a variety of different languages, and they would not have been accessible to all without a translation. Further, the early Christian evangelists could not have communicated the gospel to people in other parts of the world very easily without a shared tongue.
The prevalence of the Greek language in the Mediterranean world began with the establishment of Greek colonies, designed to enhance trade, from about 750 to 550 BC. These colonies ranged throughout the Mediterranean and Black Seas, including outposts in Spain, Gaul, Illyria, Corsica, North Africa, Egypt, Asia Minor, and elsewhere. But while Greek trade began to introduce the Greek language to the world, Greek only became the world’s dominant language through the efforts of Alexander the Great and his successors. Alexander deliberately sought to Hellenize the lands he conquered, especially by making them adopt the Greek language. Yet at one time there was no unified Greek language, for Classical Greek included a number of dialects, many of which had significant differences.
The form of Greek that the world spoke from the time of Alexander until well after the time of Christ was Koine Greek, not Classical Greek. The word Koine (κοινή) means “common”; hence, “Koine Greek” was the common dialect (κοινή διάλεκτος) of Greek. This term was first used to refer to the variety of Atticized Greek that Alexander’s army spoke as a bridge amongst the various regional dialects of Greek. As Alexander conquered Asia Minor, Syria, Palestine, Egypt, Mesopotamia, Persia, and westward past the Indus, he founded cities and outposts all along the way. Since his soldiers spoke Koine among themselves, this form of Greek became officially established in the lands Alexander conquered.
The Koine dialect had its foundations in the dominance of Athens in the fifth-century BC Delian League, in which the Athenian (Attic) dialect was imposed upon the other members of the confederacy as a lingua franca. After this, Attic Greek began to be used as a language of trade, then as a common language for military expeditions which assembled units from various parts of Greece. As a result of its common use in the business and military sectors, Attic/Koine finally began to be spoken throughout Greece as the everyday tongue of the populace, displacing other dialects. When Philip II of Macedon and his son Alexander united Greece, Koine was made the official language of the army and the royal court.
As Koine spread, it lost some of the peculiarities of the Attic dialect, and assimilated some characteristics of other dialects. This commonly involved simplification, as Koine adopted forms common to all the dialects. The use of Koine for everyday conversation rather than literature and poetry also contributed to its simplification. The development and simplification of Koine continued as it was adopted by foreigners and continuously spoken throughout the known world for hundreds of years.
As the Koine Greek language became more prevalent in the Mediterranean world, its influence also increased among the Jews. Beginning around 275 BC, a Greek translation of the Hebrew/Aramaic Old Testament was made, which we know today as the Septuagint (Seventy), abbreviated LXX (70). The influence of this translation is seen in the frequent New Testament quotations of the LXX. Most Jews who lived in the Diaspora (i.e., outside of Palestine) spoke Koine Greek as their everyday language. Even in Palestine, most Jews would have had a working knowledge of Greek, in addition to their native tongue of Aramaic.
Assigning definite dates to the period of Koine Greek is not a clear-cut matter, since languages are always changing, and these changes tend to occur gradually. However, the period of Koine can roughly be dated from 334 BC, when Alexander crossed the Hellespont, until AD 330, when the movement of the Empire’s capital from Rome to Constantinople helped to isolate West from East, and allowed for Latin to replace Greek as the lingua franca of the West—though this Latinizing process had begun as early the second century AD. The time of Koine’s widest geographical distribution and most distinctively “Koine” linguistic qualities falls in the period between these dates, in the first centuries BC and AD.
Despite the linguistic simplification that occurred in Koine, the Greek of the New Testament is still a remarkably precise and explicit language. The vocabulary, grammar, and syntax of Greek allows for precise and subtle distinctions between various forms of expression. Verbs can occur in six different tenses, four moods, and three voices, each with its own nuance. Nouns and adjectives occur in five different cases so as to specify exactly their function in the sentence and their relationship to other words. Relative and demonstrative pronouns share the number (singular/plural) and gender (masculine/feminine/neuter) of their antecedent, which removes much potential ambiguity. Further, Greek has many technical or narrowly defined terms that communicate a very precise idea.
Unlike the situation with ancient Hebrew, there is a great corpus of extrabiblical Greek literature that allows Bible scholars to see how New Testament words and grammatical constructions were employed in other literary works. Because of this, there is much more certainty about the meaning of rare words in the New Testament than there is in the Old Testament. There is also greater opportunity for scholars to do extensive research on key terms in the New Testament. An example of this is John Lee’s extensive study on the word ἕξις, which occurs only once in the New Testament (Heb 5:14), but over 6,000 times in extrabiblical Greek. Another example is Wayne Grudem’s analysis of 2,336 occurrences of the word κεφαλή (head) in selected works of Greek literature, in connection with the egalitarian feminist interpretation of 1 Corinthians 11:3 and Ephesians 5:23. While much of extent Greek literature dates from the period of Classical Greek—and therefore is less useful for comparison with the New Testament—an ample number of works survive from the time of the New Testament, including both literary works and examples of vernacular Koine from papyrus letters.
Unlike in the Old Testament, the Greek style of the New Testament varies considerably among its writers and books. This is partly because many New Testament books were originally letters, and were not primarily written as literary works. Variation in style also occurs because of different personal writing styles, and different levels of familiarity with the Greek language. The most polished, Classical-style Greek of the New Testament is found in the book of Acts, which was written by Luke (a Gentile medical doctor). John’s Greek is the simplest and most non-native, though this does not mean that his content is simplistic. Many New Testament books use the kind of Greek that educated people would have used in letters. It should be noted that the New Testament was written on a literary level, and not on the level of vernacular speech—just as an educated English-speaker uses a more formal and proper form of the language when writing a document than when speaking to friends. The literary style of the New Testament ranges from that of a formal letter to that of a formal narrative or treatise.
The Greek of the New Testament has a heavily Semitic coloring, due in part to the influence of the Hebrew Old Testament on the New Testament and Christianity. In addition, since Aramaic was widely spoken in Palestine and Syria, the common Greek of Palestine and Syria contained Aramaic influences. Aramaic was the mother tongue of Jesus and most of the apostles. Thus, one frequently finds the word “hour” used in the sense of “moment” in the New Testament, which is an Aramaism (cf. Acts 16:18). The frequent use of the descriptive term “son of” is also an Aramaism (cf. Mark 3:17). One often finds the Greek words καί and δέ used like the Hebrew conjunction wāw in New Testament narratives, especially in the Gospel of Mark. There are even some examples of Greek words used with Semitic grammar, especially in quotations of the Old Testament and in the book of Revelation. For this reason, anyone who wants to be an expert in the Greek of the New Testament must also have a working knowledge of Hebrew and Aramaic.
Jesus Christ came into the world at a time when there was a universal language. Because Koine Greek was understood by everyone, most early Christian missionaries spread the gospel in this language, and the whole New Testament was written in this language. Even New Testament books that were sent to Palestine (James, Hebrews) or Rome (Mark, Romans) were written in Koine Greek, since this language was understood by everyone. It was spoken by men of all races, geographic locales, and societal classes, from slaves and common laborers to kings and intellectuals. To summarize: Koine Greek was the world’s universal language.
 John A. L. Lee, “Hebrews 5:14 and Ἕξις: A History of Misunderstanding,” NovT 39:2 (Apr. 1997): 151-76.
 Wayne Grudem, “Does Κεφαλή (‘Head’) mean ‘Source’ or ‘Authority Over’ in Greek Literature? A Survey of 2,336 Examples,” TrinJ 6:1 (Spr. 1985): 38-59.