The New Testament of the Bible was written in Greek because Greek was the linga franca, or common language, of the Roman Empire. As a result, the authors of wrote in Greek even when it wasn’t the language they spoke, ensuring that their manuscripts could be widely read and passed on to future generations. Greek probably became the Roman lingua franca as a result of the empire of Alexander the Great, a Greek military leader who conquered a large section of the Ancient World, introducing people to the language.
Written over a period of around 100 years, the New Testament documents the early stages of Christianity, including the birth of Christ and His teachings and ministry. For many Christians, it forms an important part of their personal faith, with people turning to it to hear the words of Christ as recorded by His followers, and to learn more about the evolution of Christianity. The Old Testament, the first section of the Bible, is much older, and it was written in Hebrew. Christ was undoubtedly familiar with the Old Testament, as were many of His contemporaries.
The form of Greek used to write the New Testament is known as Koine or Common Greek, and it represents an evolutionary step between Ancient Greek and its Modern Version, meaning that people must learn Koine Greek specifically if they want to read the document in its original language. In many parts of the Roman Empire, Koine Greek was actually the official language, rather than Latin, because its use was so widespread. Some scholars refer to Koine Greek as Biblical Greek, in a reference to its arguably most famous application.
Christ Himself, along with His contemporaries, would have spoken Aramaic. The choice to use Koine Greek was probably motivated by the desire to spread Christianity in a common and well understood language. There is also some argument about whether the entire New Testament was written in Greek, as some evidence suggests that portions may have been written in Aramaic or Hebrew and translated later.
Many translations have been produced, with scholars referring both to the original Koine Greek text and later translations and commentaries. The translation of the Bible has not been without controversy. Some people believe that translation changes the meaning of the text, and that true believers should read the Bible in its original language.