Biblical Greek, or koine Greek, was the common Greek language that was spoken and written during the Hellenistic period, the Roman Empire, and the early Byzantine Empire. It eventually developed into the current modern day Greek that is spoken today.
There is a fair amount of debate as to how biblical Greek should be pronounced. Western scholars will often argue for a pronunciation that is thought to be a reconstruction of koine Greek. This is what is frequently taught in academic settings in the West. In Greece and in eastern churches that still actively use and read the biblical texts in Greek, you will hear the modern Greek pronunciation.
For this podcast, I use the modern Greek pronunciation because that is what I hear in my parish, and I frequently encounter native Greek speakers who use this pronunciation when reading from the biblical texts. Modern Greek is, therefore, “functional” for me. A reconstructed pronunciation that does not sound like that which is used in faith communities where Greek is still “living” and functional would decrease comprehension drastically. I believe, however, that the most important reason for studying biblical Greek is so that the modern day reader can understand what the original authors were trying to communicate. Getting wrapped up in the “correct“ pronunciation can ultimately be a distraction from this end goal.