When did genuine and spurious diphthongs merge?

This merger is thought to have happened in the 5th-4th centuries BC.

1. What is Ancient Greek spurious diphthongs?
2. How is ancient and modern Greek phonology different?
3. Did Ancient Greek have a soft C sound?
4. What is the combination of two vowel sounds?

What is Ancient Greek spurious diphthongs?

A spurious diphthong (or false diphthong) is an Ancient Greek vowel that is etymologically a long vowel but written exactly like a true diphthong ει, ου (ei, ou).

How is ancient and modern Greek phonology different?

Attic Greek had about 15 consonant phonemes: nine stop consonants, two fricatives, and four or six sonorants. Modern Greek has about the same number of consonants. The main difference between the two is that Modern Greek has voiced and voiceless fricatives that developed from Ancient Greek voiced and aspirated stops.

Did Ancient Greek have a soft C sound?

(This is quite unhistorical; in ancient times all "c"s were hard, but we are used to pronouncing "Caesar," "Circe," etc. with a soft "c.") The same applies to "g"; soft (as in "giant") before "e" and "i" sounds, hard (as in "gate") otherwise.

What is the combination of two vowel sounds?

A diphthong is a sound made by combining two vowels, specifically when it starts as one vowel sound and goes to another, like the oy sound in oil.