Vowel harmony is a type of long-distance (see below) assimilatory phonological process involving vowels in some languages. In languages with vowel harmony, there are constraints on what vowels may be found near each other.
Harmony processes are "long-distance" in the sense that the assimilation involves sounds that are separated by intervening segments (usually consonant segments). In other words, harmony refers to the assimilation of sounds that are not adjacent to each other. For example, a vowel at the beginning of a word can trigger assimilation in a vowel at the end of a word. The assimilation sometimes occurs across the entire word. This is represented schematically in the following diagram:
|VaCVbCVbC||→||VaCVaCVaC||(Va = type-a vowel, Vb = type-b vowel, C = consonant)|
In the diagram above, the Va (type-a vowel) causes the following Vb (type-b vowel) to assimilate and become the same type of vowel (and thus they become, metaphorically, "in harmony").
The vowel that causes the vowel assimilation is frequently termed the trigger while the vowels that assimilate (or harmonize) are termed targets. In most languages, the vowel triggers lie within the root of a word while the affixes added to the roots contain the targets. This may be seen in the Hungarian dative suffix:
The dative suffix has two different forms -nak/-nek. The -nak form appears after the root with back vowels (a and o are both back vowels). The -nek form appears after the root with front vowels (ö and e are front vowels).
Another example: Turkish araba (car) pluralises to arabalar but tren (train) pluralises to trenler.
Harmony assimilation may spread either from the beginning of the word to the end or from the end to the beginning. Progressive harmony (a.k.a. left-to-right harmony) proceeds from beginning to end; regressive harmony (a.k.a. right-to-left harmony) proceeds from end to beginning. Languages that have both prefixes and suffixes often have both progressive and regressive harmony. Languages that primarily have prefixes (and no suffixes) usually have only regressive harmony — and vice versa for primarily suffixing languages.
Vowel harmony often involves dimensions such as
In many languages, vowels can be said to belong to particular classes, such as back vowels or rounded vowels, etc. Some languages have more than one system of harmony. For instance, Altaic languages have a rounding harmony superimposed over a backness harmony.
In some languages, not all vowels participate in the vowel conversions — these vowels are termed either neutral or transparent. Intervening consonants are also often transparent. In addition to these transparent segments, many languages have opaque vowels that block vowel harmony processes.
Finally, languages that do have vowel harmony sometimes have words that fail to harmonize. This is known as disharmony. Many loanwords exhibit disharmony, either within a root (e.g., Turkish/Turkic vakit/waqit, "time" [from Arabic waqt], where °vakıt/°waqıt would have been expected) or in suffixes (e.g., Turkish saat-ler "(the) hours" [hour-PL, from Arabic sâ`a], where saat-lar would have been expected). In Turkish, disharmony tends to disappear through analogy, especially within loanwords. Suffixes drop disharmony to a lesser extent, e.g. Hüsnü (a man's name) < previously Hüsni, from Arabic husnî; müslümân "Moslem, Muslim (adj. and n.)" < °müslimân, from Arabic muslim).
In the first sense, vowel harmony refers to any type of vowel harmony: that is, both progressive and regressive vowel harmony. When used in this sense, the term vowel harmony is synonymous with the term metaphony.
In the second sense, vowel harmony refers only to progressive vowel harmony (beginning-to-end). For regressive harmony, the term umlaut is used. In this sense, metaphony is the general term while vowel harmony and umlaut are both sub-types of metaphony. (Note that the term umlaut is also used in a different sense to refer to a type of vowel gradation.)
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.
Vowel harmony is a grammaticalized feature of phonotactics, thus it may not work as expected from pure phonology, 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 pronounced olumpia. The position of some loans is unstandardized (e.g. chattailla/chättäillä ) or ill-standardized (e.g. polymeeri, 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 counts. For example, Olympiassa the initial syllable o- would require the final vowel to be -ä, but there is an intervening -y-, so that the final -a counts.
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". If fusion takes place, the vowel is harmonized by some speakers, e.g. tälläinen pro tällainen ← tämän lainen.
|Back ("low")||a á||o ó||u ú|
|e é||i í|
|rounded||ö ő||ü ű|
The only essential difference in classification between Hungarian and Finnish is that Hungarian does not observe the difference between Finnish 'ä' [æ] and 'e' [e] the Hungarian front vowel 'e' [æ] is the same as the Finnish front vowel 'ä'.
The suffix rules for words with both kinds of suffixes are the following:
|-kor(at, for time)||-ban/-ben(in)||-hoz/-hez/-höz(to)|
|Back|| hat (6)|
|Front||unrounded(neutral)|| egy (1)|
|rounded|| öt (5)|
In vowels in suffixes must harmonize with either /u/ or its non-/u/ counterparts or with /ɔ/ or non-/ɔ/ counterparts. For example, the vowel in the aorist suffix appears as /u/ when it follows a /u/ in the root, but when it follows all other vowels it appears as /i/. Similarly, the vowel in the nondirective gerundial suffix appears as /ɔ/ when it follows a /ɔ/ in the root; otherwise it appears as /a/.
|gophin||[ɡɔphin]||'take of infant (aorist)'|
|-tow/-taw||(nondirective gerundial suffix)|
|goptow||[ɡɔptɔw]||'take care of infant (nondir. ger.)'|
|giy̓taw||[ɡij’taw]||'touch (nondir. ger.)'|
|muṭtaw||[muʈtaw]||'swear (nondir. ger.)'|
|xattaw||[xatːaw]||'eat (nondir. ger.)'|
In addition to the harmony found in suffixes, there is a harmony restriction on word stems where in stems with more than one syllable all vowels are required to be of the same lip rounding and tongue height dimensions. For example, a stem must contain all high rounded vowels or all low rounded vowels, etc. This restriction is further complicated by (i) long high vowels being lowered and (ii) an epenthetic vowel [i] which does not harmonize with stem vowels.
|Positive/"light"/Yang Vowels||ㅏ (a)||ㅑ (ya)||ㅗ (o)||ㅛ (yo)|
|ㅐ (ae)||ㅘ (wa)||ㅚ (oe)||ㅙ (wae)|
|Negative/"heavy"/Yin Vowels||ㅓ (eo)||ㅕ (yeo)||ㅜ (u)||ㅠ (yu)|
|ㅔ (e)||ㅝ (wo)||ㅟ (wi)||ㅞ (we)|
|Neutral/Centre Vowels||ㅡ (eu)||ㅣ (i)||ㅢ (ui)|
There are three classes of vowels in Korean: positive, negative, and neutral. These categories loosely follow the front (positive) and mid (negative) vowels. Traditionally, Korean had strong vowel harmony; however, this rule is no longer observed strictly in modern Korean. In modern Korean, it is only applied in certain cases such as onomatopoeia, adjectives, adverbs, conjugation, and interjections. The vowel ㅡ(eu) is considered a partially neutral and a partially negative vowel. There are other traces of vowel harmony in modern Korean: many native Korean words tend to follow vowel harmony such as 사람 (saram), which means person, and 부엌 (Bueok), which means kitchen.
Proponents of Korean as an Altaic language use the existence of vowel harmony in Korean to support their argument.
Although vowel harmony is the most well-known harmony, not all types of harmony that occur in the world's languages involve only vowels. Other types of harmony involve consonants (and is known as consonant harmony). Rarer types of harmony are those that involve tone or both vowels and consonants (e.g. postvelar harmony).
Some languages have harmony processes that involve an interaction between vowels and consonants. For example, Chilcotin has a phonological process known as vowel flattening (i.e. post-velar harmony) where vowels must harmonize with uvular and pharyngealized consonants.
Chilcotin has two classes of vowels:
Additionally, Chilcotin has a class of pharyngealized "flat" consonants . Whenever a consonant of this class occurs in a word, all preceding vowels must be flat vowels.
|[jətʰeɬʦˤʰosˤ]||'he's holding it (fabric)'|
|[natʰák’ə̃sˤ]||'he'll stretch himself'|
If flat consonants do not occur in a word, then all vowels will be of the non-flat class:
|[nænɛntʰǽsʊç]||'I'll comb hair'|
|[tetʰǽsk’ɛn]||'I'll burn it'|
Other languages of this region of North America (the Plateau culture area), such as St'át'imcets, have similar vowel-consonant harmonic processes.