This is called vowel harmony and it's a fairly common linguistic feature: https://en.wikipedia.org/wiki/Vowel_harmony https://en.wikipedia.org/wiki/Vowel_harmo

This is called vowel harmony and it's a fairly common linguistic feature: https://en.wikipedia.org/wiki/Vowel_harmony https://en.wikipedia.org/wiki/Vowel_harmony ...but it's notably absent from the Indo-European languages.