Complex sentence: During the period generally designated as Koine Greek, a great deal of phonological change occurred: at the start of the period, the pronunciation was virtually identical to Ancient Greek phonology, whereas in the end it had much more in common with Modern Greek phonology.
Split into simpler sentences: During the period generally designated as Koine Greek a great deal of phonological change occurred. At the start of the period pronunciation was virtually identical to Ancient Greek phonology, whereas in the end it had much more in common with Modern Greek phonology.