äänenkulkuun
Äänenkulkuun is a Finnish term that translates to "vowel harmony" in English. It is a phonological phenomenon found in many Uralic languages, including Finnish, Estonian, and Hungarian. Vowel harmony dictates that all vowels within a word, including suffixes, must belong to the same class. Typically, this classification is based on the position of the tongue during vowel production: front vowels (ä, ö, y) and back vowels (a, o, u). Some languages also include neutral vowels (i, e) which can appear with either front or back vowels.
In Finnish, for instance, a word can either contain only front vowels (e.g., "metsässä" - in the forest)