Complex sentence: The Greek language underwent pronunciation changes during the Koine Greek period, from about 300 BC to 300 AD from almost identical to Classical Greek, while at the end it was closer to Modern Greek.
Split into simpler sentences: The Greek language underwent pronunciation changes during the Koine Greek period, from about 300 BC to 300 AD. At the beginning of the period, the pronunciation was almost identical to Classical Greek, while at the end it was closer to Modern Greek.