The language of the NT writings was a development of classical (Attic) Greek, much as modern English has changed since the publication of AV in 1611. Greek had become a lingua franca through the civilized world in the 1st cent. and it was essential equipment for trade and communication. It was therefore the language used by the four evangelists, and by Josephus and Philo. Even in Rome itself Greek was in general use, Latin being the language of the upper classes engaged in law and administration. Greek of this period is called koine, or common, Greek and some of those who spoke it adulterated it with idioms from their first language. In the gospels a few scraps of the original Aramaic which Jesus spoke have been preserved in a Greek form, and some NT concepts expressed in Greek have to be understood against this OT background (e.g. ‘righteousness’), though it is incorrect as a normal principle simply to explain Greek NT concepts in terms of the Hebrew OT.
Greek has seven vowels, since e and o can both be either short (as English ‘empty’ or long as in ‘me’), and this distinction should be represented in public reading of the NT as in Ōmĕga (Rev. 1: 8). Normally a final -e in a proper noun (as in Phoeb-ē, Rom. 16: 1, or Eunic-ē, 2 Tim. 1: 5) is long.