Noun
vowel harmony (usually uncountable, plural vowel harmonies)
(phonology) A phonological process in some languages that sets constraints on which vowels may be found near each other or within a word, such as back vowels or front vowels; sometimes resulting in variant affixes, clitics or similar variations.
Vowel harmony is an important aspect of Mongolian.
As a consequence, Finnish speakers often have problems with pronouncing foreign words which do not obey vowel harmony. Source: Internet
Even among languages with vowel harmony, not all vowels need participate in the vowel conversions; these vowels are termed neutral. Source: Internet
Finally, languages that do have vowel harmony often allow for lexical disharmony, or words with mixed sets of vowels even when an opaque neutral vowel is not involved. Source: Internet
From vowel harmony it follows that the initial syllable of each single (non-compound) word controls the frontness or backness of the entire word. Source: Internet
Helsinki slang has slang words that have roots violating vowel harmony, e.g. Sörkka. Source: Internet
In standard Finnish, these words are pronounced as they are spelled, but many speakers apply vowel harmony – olumpialaiset, and sekundaarinen or sekyndäärinen. Source: Internet