Vokaaliharmonia

Finnish

	Neutral		Front	Back
High	i		y	u
Mid	e		ö	o
Low			ä	a

In the Finnish language, there are three classes of vowels – front, back, and neutral, where each front vowel has a back vowel pairing. Grammatical endings such as case and derivational endings – but not enclitics – have only archiphonemic vowels A, U, O, which are realized as either back [u, o, a] or front [y, ø, æ] inside a single word. From vowel harmony it follows that the initial syllable of each single (non-compound) word controls the frontness or backness of the entire word. Non-initially, the neutral vowels are transparent to and unaffected by vowel harmony. In the initial syllable:

1. a back vowel causes all non-initial syllables to realize with back (or neutral) vowels, e.g. pos+ahta+(t)a → posahtaa
2. a front vowel causes all non-initial syllables to realize with front (or neutral) vowels, e.g. räj+ahta+(t)a → räjähtää.
3. a neutral vowel acts like a front vowel, but does not control the frontness or backness of the word: if there are back vowels in non-initial syllables, the word acts like it began with back vowels, even if they come from derivational endings, e.g. sih+ahta+(ta) → sihahtaa cf. sih+ise+(t)a → sihistä

For example:

• kaura begins with back vowel → kauralla
• kuori begins with back vowel → kuorella
• sieni begins without back vowels → sienellä (not *sienella)
• käyrä begins without back vowels → käyrällä
• tuote begins with back vowels → tuotteeseensa
• kerä begins with a neutral vowel → kerällä
• kera begins with a neutral vowel, but has a noninitial back vowel → keralla

Some dialects that have a sound change opening diphthong codas also permit archiphonemic vowels in the initial syllable. For example, standard 'ie' is reflected as 'ia' or 'iä', controlled by noninitial syllables, in the Tampere dialect, e.g. tiä ← tie but miakka ← miekka.
... as evidenced by tuotteeseensa (not *tuotteeseensä). Even if phonologically front vowels precede the suffix -nsa, grammatically it is preceded by a back vowel-controlled word. As shown in the examples, neutral vowels make the system unsymmetrical, as they are front vowels phonologically, but leave the front/back control to any grammatical front or back vowels. There is little or no change in the actual vowel quality of the neutral vowels.
As a consequence, Finnish speakers often have problems with pronouncing foreign words which do not obey vowel harmony. For example, olympia is often pronounced olumpia. The position of some loans is unstandardized (e.g. chattailla/chättäillä ) or ill-standardized (e.g. polymeeri, sometimes pronounced polumeeri, and autoritäärinen, which violate vowel harmony). Where a foreign word violates vowel harmony by not using front vowels because it begins with a neutral vowel, then last syllable generally counts, although this rule is irregularly followed.^[4] Experiments indicate that e.g. miljonääri always becomes (front) miljonääriä, but marttyyri becomes equally frequently both marttyyria (back) and marttyyriä (front), even by the same speaker.
With respect to vowel harmony, compound words can be considered separate words. For example, syyskuu ("autumn month" i.e. September) has both u and y, but it consists of two words syys and kuu, and declines syys·kuu·ta (not *syyskuutä). The same goes for enclitics, e.g. taaksepäin "backwards" consists of the word taakse "to back" and -päin "-wards", which gives e.g. taaksepäinkään (not *taaksepäinkaan or *taaksepainkaan). If fusion takes place, the vowel is harmonized by some speakers, e.g. tälläinen pro tällainen ← tämän lainen.
Helsinki slang has slang words that have roots violating vowel harmony, e.g. Sörkka. This can be interpreted as Swedish influence.