Phonology
A series of radical sound shifts, which the Greek language underwent mainly during the period of Koine, has led to a phonological system in Modern Greek that is significantly different from that of Ancient Greek. Instead of the rich vowel system of Ancient Greek, with its four vowel-height levels, length distinction, and multiple diphthongs, Modern Greek has a very simple system of five vowels. This came about through a series of mergers, especially towards /i/ (iotacism). In the consonants, Modern Greek has two series of fricatives in lieu of the Ancient Greek voiced and aspirated voiceless plosives. Modern Greek has not preserved length distinctions, either in the vowels or in the consonants.
Read more about this topic: Modern Greek