Ääniharmonia

Ääniharmonia, also known as vowel harmony, is a phonological process found in many agglutinative languages, particularly those of the Turkic, Uralic, and Tungusic families. It dictates that vowels within a word, or sometimes across word boundaries, must belong to a specific set of categories. Typically, this harmony is based on features such as frontness/backness or roundedness of vowels.

For instance, in Finnish, a Uralic language, vowels are broadly classified as front (ä, ö, y) or back (a, o, u). A word can generally only contain front vowels or back vowels, not a mixture. Suffixes in Finnish also change their vowel to match the vowel class of the word stem. For example, the partitive singular suffix is -a/-ä, and it will be -a if the stem contains back vowels and -ä if the stem contains front vowels.

Turkish, a Turkic language, exhibits a more complex system of vowel harmony, often involving both front/back and rounded/unrounded features. A word might contain only front vowels (e, i, ö, ü) or only back vowels (a, ı, o, u), and suffixes will adapt their vowels accordingly. This creates a distinct sonic quality to languages that employ it, making them sound more melodious or unified to some listeners. The specific rules and the extent to which harmony applies can vary significantly between different languages.