Vowel

In phonetics, a vowel is a sound in spoken language that is characterized by an open configuration of the vocal tract so that there is no build-up of air pressure above the glottis. This contrasts with consonants, which are characterized by a constriction or closure at one or more points along the vocal tract. A vowel is also understood to be syllabic: an equivalent open but non-syllabic sound is called a semivowel.

In all languages, vowels form the nucleus or peak of syllables, whereas consonants form the onset and (in languages which have them) coda. However, some languages also allow other sounds to form the nucleus of a syllable, such as the syllabic l in the English word table (the stroke under the l indicates that it is syllabic; the dot separates syllables), or the r in the Czech word vrba  "willow".

The word vowel comes from the Latin word vocalis, meaning "speaking", because in most languages words and thus speech are not possible without vowels.

Articulation
The articulatory features that distinguish different vowels in a language are said to determine the vowel's quality. Daniel Jones developed the cardinal vowel system to describe vowels in terms of the common features height (vertical dimension), backness (horizontal dimension) and roundedness (lip position). These three parameters are indicated in the schematic IPA vowel diagram on right. There are however still more possible features of vowel quality, such as the velum position (nasality), type of vocal fold vibration (phonation), and tongue root position.

Height
Height refers to the vertical position of the tongue relative to either the roof of the mouth or the aperture of the jaw. In high vowels, such as [ i ] and [ u ], the tongue is positioned high in the mouth, whereas in low vowels, such as [ a ] , the tongue is positioned low in the mouth. Sometimes the terms open and close are used as synonyms for low and high for describing vowels. The International Phonetic Alphabet identifies seven different vowel heights, although no known language distinguishes all seven:


 * close vowel (high vowel)
 * near-close vowel
 * close-mid vowel
 * mid vowel
 * open-mid vowel
 * near-open vowel
 * open vowel (low vowel)

It may be that some varieties of German have five contrasting heights. The Bavarian dialect of Amstetten has thirteen long vowels, reported to be distinguished as four heights (close, close-mid, mid, and near-open) among the front unrounded, front rounded, and back rounded vowels, plus an open central vowel:. Otherwise, the usual limit on the number of vowel heights is four.

The parameter of vowel height appears to be the most primary feature of vowels cross-linguistically in that all languages use height contrastively. The other possible parameters, such as backness and roundedness (explained below), are not used in all languages.

Backness
Backness refers to the horizontal tongue position during the articulation of a vowel relative to the back of the mouth. In front vowels, such as, the tongue is positioned forward in the mouth, whereas in back vowels, such as , the tongue is positioned towards the back of the mouth. The International Phonetic Alphabet identifies five different degrees of vowel backness, although no known language distinguishes all five:
 * front vowel
 * near-front vowel
 * central vowel
 * near-back vowel
 * back vowel

The highest number of constrastive degrees of backness is 3.

Roundedness
Roundedness refers to whether the lips are rounded or not. In most languages, roundedness is a reinforcing feature of mid to high back vowels, and not distinctive. Usually the higher a back vowel, the more intense the rounding. However, some languages treat roundedness and backness separately, such as French and German (with front rounded vowels), most Uralic languages (Estonian has a rounding contrast for /o/ and front vowels), Turkic languages (with an unrounded /u/), Vietnamese (with back unrounded vowels), and Korean (with a contrast in both front and back vowels).

Nonetheless, even in languages such as German and Vietnamese, there is usually some correlation between rounding and backness: Front rounded vowels tend to be less front than front unrounded vowels, and back unrounded vowels tend to be less back than back rounded vowels. That is, the placement of unrounded vowels to the left of rounded vowels on the IPA vowel chart is reflective of their typical position.

Different kinds of labialization are also possible. The Japanese /u/, for example, is not rounded like English /u/, where the lips are protruded (or pursed), but neither are the lips spread to the sides as they are for unrounded vowels. Rather, they are compressed in both directions, leaving a slot between the lips for the air to escape. (See Vowel roundedness for illustrations.) Swedish is one of the few languages where this feature is contrastive, have both protruded-lip and compressed-lip high front vowels. In many treatments, both are considered a type of rounding, and are often called endolabial rounding (pursed, where the insides of the lips approach each other) and exolabial rounding (compressed, where the margins of the lips approach each other). However, other phoneticians do not believe that these are subsets of a single phenomenon of rounding, and prefer instead the three independent terms rounded, compressed, and spread (for unrounded).

Nasalization
Nasalization refers to whether some of the air escapes through the nose. In nasal vowels, the velum is lowered, and some air travels through the nasal cavity as well as the mouth. An oral vowel is a vowel in which all air escapes through the mouth. French, Polish and Portuguese contrast nasal and oral vowels.

Phonation
Voicing describes whether the vocal cords are vibrating during the articulation of a vowel. Most languages only have voiced vowels, but several Native American languages, such as Cheyenne and Totonac, contrast voiced and devoiced vowels. Vowels are devoiced in whispered speech. As in Japanese and Quebec French, vowels that are between voiceless consonants are often devoiced.

Modal voice, creaky voice, and breathy voice (murmured vowels) are phonation types that are used contrastively in some languages. Often, these co-occur with tone or stress distinctions; in the Mon language, vowels pronounced in the high tone are also produced with creaky voice. In cases like this, it can be unclear whether it is the tone, the voicing type, or the pairing of the two that is being used for phonemic contrast. This combination of phonetic cues (i.e. phonation, tone, stress) is known as register or register complex.

Tongue root retraction
Advanced tongue root (ATR) is a feature common across much of Africa. The contrast between advanced and retracted tongue root resembles the tense/lax contrast acoustically, but they are articulated differently. ATR vowels involve noticeable tension in the vocal tract.

Secondary narrowings in the vocal tract
Pharyngealized vowels occur in some languages; Sedang uses this contrast, as do the Tungusic languages. Pharyngealisation is similar in articulation to retracted tongue root, but is acoustically distinct.

A stronger degree of pharyngealisation occur in the Northeast Caucasian languages and the Khoisan languages. These might be called epiglottalized, since the primary constriction is at the tip of the epiglottis.

The greatest degree of pharyngealisation is found in the strident vowels of the Khoisan languages, where the larynx is raised, and the pharynx constricted, so that either the epiglottis or the arytenoid cartilages vibrate instead of the vocal chords.

Note that the terms pharyngealized, epiglottalized, strident, and sphincteric are sometimes used interchangeably.

Rhotic vowels
Rhotic vowels are the "ar-colored vowels" of English and a few other languages.

Tenseness/checked vowels vs. free vowels
Tenseness is used to describe the opposition of tense vowels as in leap, suit vs. lax vowels as in lip, soot. This opposition has traditionally been thought to be a result of greater muscular tension, though phonetic experiments have repeatedly failed to show this.

Unlike the other features of vowel quality, tenseness is only applicable to the few languages that have this opposition (mainly Germanic languages, e.g. English), whereas the vowels of the other languages (e.g. Spanish) cannot be described with respect to tenseness in any meaningful way.

In most Germanic languages, lax vowels can only occur in closed syllables. Therefore, they're also known as checked vowels, whereas the tense vowels are called free vowels since they can occur in any kind of syllable.

Acoustics


The acoustics of vowels are fairly well-understood. The different vowel qualities are realized in acoustic analyses of vowels by the relative values of the formants, acoustic resonances of the vocal tract which show up as dark bands on a spectrogram. The vocal tract acts as a resonant cavity, and the position of the jaw, lips, and tongue affect the parameters of the resonant cavity, resulting in different formant values. The acoustics of vowels can be visualized using spectrograms, which display the acoustic energy at each frequency, and how this changes with time.

The first formant, abbreviated "F1", corresponds to vowel openness (vowel height). Open vowels have high F1 frequences while close vowels have low F1 frequencies, as can be seen at right: The and  have similar low first formants, whereas  has a higher formant.

The second formant, F2, corresponds to vowel frontness. Back vowels have low F2 frequencies while front vowels have high F2 frequencies. This is very clear at right, where the front vowel has a much higher F2 frequency than the other two vowels. However, in open vowels the high F1 frequency forces a rise in the F2 frequency as well, so a better measure of frontness is the difference between the first and second formants. For this reason, vowels are usually plotted as F1 vs. F2 – F1. This is the case for the vowel chart at the top of this page. (This dimension is usually called 'backness' rather than 'frontness', but the term 'backness' can be counterintuitive when discussing formants.)

R-colored vowels are characterized by lowered F3 values.

Rounding is generally realized by a complex relationship between F2 and F3 that tends to reinforce vowel backness. One effect of this is that back vowels are most commonly rounded while front vowels are most commonly unrounded; another is that rounded vowels tend to plot to the right of unrounded vowels in vowel charts. That is, there is a reason for plotting vowel pairs the way they are.

Prosody and intonation
The features of vowel prosody are often described independently from vowel quality. In non-linear phonetics, they are located on parallel layers. The features of vowel prosody are usually considered not to apply to the vowel itself, but to the syllable, as some languages do not contrast vowel length separately from syllable length.

Intonation encompasses the changes in pitch, intensity, and speed of an utterance over time. In tonal languages, in most cases the tone of a syllable is carried by the vowel, meaning that the relative pitch or the pitch contour that marks the tone is superimposed on the vowel. If a syllable has a high tone, for example, the pitch of the vowel will be high. If the syllable has a falling tone, then the pitch of the vowel will fall from high to low over the course of uttering the vowel.

Length or quantity refers to the abstracted duration of the vowel. In some analyses this feature is described as a feature of the vowel quality, not of the prosody. Japanese, Finnish, Hungarian, Arabic and Latin have a two-way phonemic contrast between short and long vowels. The Mixe language has a three-way contrast among short, half-long, and long vowels, and this has been reported from a few other languages, in not all of which is the distinction phonemic. Long vowels are written in the IPA with a triangular colon, which has two equilateral triangles pointing at each other in place of dots. The IPA symbol for half-long vowels is the top half of this. Longer vowels are sometimes claimed, but these are always divided between two syllables.

It should be noted that the length of the vowel is a grammatical abstraction, and there may be more phonologically distinctive lengths. For example, in Finnish, there are five different physical lengths, because stress is marked with length on both grammatically long and short vowels. However, Finnish stress is not lexical and is always on the first two moras, thus this variation serves to separate words from each other.

In non-tonal languages, like English, intonation encompasses lexical stress. A stressed syllable will typically be pronounced with a higher pitch, intensity, and length than unstressed syllables. For example in the word intensity, the vowel represented by the letter 'e' is stressed, so it is longer and pronounced with a higher pitch and intensity than the other vowels.

Monophthongs, diphthongs, triphthongs
A vowel sound whose quality doesn't change over the duration of the vowel is called a monophthong. Monophthongs are sometimes called "pure" or "stable" vowels. A vowel sound that glides from one quality to another is called a diphthong, and a vowel sound that glides between three qualities is a triphthong.

All languages have monophthongs and many languages have diphthongs, but triphthongs or vowel sounds with even more target qualities are relatively rare cross-linguistically. English has all three types: the vowel sound in hit is a monophthong, the vowel sound in boy is in most dialects a diphthong , and the vowel sounds of way , flower (BrE AmE ) form a triphthong (dissylabic in the latter cases), although the particular qualities vary by dialect.

The longest sensible word with most consecutive vowels is Finnish riiuuyöaieuutinen (courting night intention news [certainly yellow press stuff!]), syllabicated rii-uu-yö-ai-e-uu-ti-nen.

In phonology, diphthongs and triphthongs are distinguished from sequences of monophthongs by whether the vowel sound may be analyzed into different phonemes or not. For example, the vowel sounds in a two-syllable pronunciation of the word flower (BrE AmE ) phonetically form a dissyllabic triphthong, but are phonologically a sequence of a diphthong (represented by the letters ) and a monophthong (represented by the letters ). Some linguists use the terms diphthong and triphthong only in this phonemic sense.

Vowels in languages
The semantic significance of vowels varies widely depending on the language. In some languages, particularly Semitic languages, vowels mostly serve to denote inflections. This is similar to English man vs. men. In fact, the alphabets used to write the Semitic languages, such as the Hebrew alphabet and the Arabic alphabet, do not ordinarily mark all the vowels. These alphabets are called abjads. Although it is possible to construct simple English sentences that can be understood without written vowels (cn y rd ths?), extended passages of English lacking written vowels are difficult if not impossible to completely understand (consider dd, which could be any of add, aided, dad, dada, dead, deed, did, died, dodo, dud, dude, eddie, iodide, or odd).

In most languages, vowels are an unchangeable part of the words, as in English man vs. moon which are not different inflectional forms of the same word, but different words. Vowels are especially important to the structures of words in languages that have very few consonants (like Polynesian languages such as Maori and Hawaiian), and in languages whose inventory of vowels is larger than its inventory of consonants.

Vowel systems
Most languages have 3–7 vowels, the following 5-vowel system being the most common:

This configuration is often thought to be particularly stable because it makes efficient use of the vowel space, in that slight variations in one vowel are not confused for another vowel. Spanish and Modern Greek, for example, have this vowel system; Latin had a similar system with the addition of (unwritten) vowel length; it is for this reason that the Latin alphabet has five vowel letters.

All known languages have at least two vowels: Abxaz, Margi, Eastern Arrernte, and perhaps some of the Ndu languages contrast only two vowels: and  in the case of Margi, and  and  for the others, with significant allophony. There have been proposals to reduce the three-vowel inventory of Kabardian to two, one, or even zero vowels (in which case all phonetic vowels would be epenthetic), but most linguists do not believe such analyses are workable.

Three-vowel systems have been noted in a large number of languages. These include,


 * /i, a, u/ (Arabic, Inuktitut, Quechua, Malay, and most of the Australian languages),
 * /i, a, o/ (Pirahã),
 * /ɨ, ə, aː/ (Kabardian),
 * /i, e, a/ (Wichita).

A fair number of Native American languages, such as Nahuatl and Navajo, have four-vowel systems that lack /u/, but there is no known language that lacks some form of a. At the other end of the spectrum, languages with more than twelve vowels are uncommon, although some widely-spoken languages have large vowel inventories, particularly Germanic languages. For example, English has 14–20 vowels (including diphthongs) depending on dialect, and Swedish has 17 distinct vowel qualities in the height-backness-roundedness spectrum, although these also involve a length contrast, and the long vowels have diphthongized allophones. French has 16 vowel qualities, including nasals, and the previously-mentioned Sedang has 24 distinct monophthongs, which it achieves by contrasting phonation on seven vowel qualities. Ju/’hoan uses phonation and nasalization with five vowel qualities to achieve approximately 40 vowels, most of which may in addition occur both long and short.

Written vowels
The name "vowel" is often used for the symbols used for representing vowel sounds in a language's writing system, particularly if the language uses an alphabet. In the Latin alphabet, the vowel letters are A, E, I, O, U, and Y; in addition, extensions of the Latin alphabet have independent vowel letters such as Ä, Ö, Ü, Å, &AElig;, and &Oslash;. The phonetic values vary by language, and some languages use I and Y for the consonant [j], e.g. initial I in Romanian and initial Y in in English. The syllable nucleus may also be a semivowel, like 'W'' in Welsh.

There is not necessarily a direct one-to-one correspondence between the vowel sounds of a language and the vowel letters. Many languages that use a form of the Latin alphabet have more vowel sounds than can be represented by the standard set of five vowel letters. In the case of English, the five primary vowel letters can represent both long and short vowel sounds (some of the long vowel sounds in English are actually diphthongs). Furthermore, in English some vowel sounds are represented by combinations of vowel letters, such as the ea in beat or by a vowel letter and an approximant letter, as the ow in how, or the er in her.

Other languages cope with the limitation in the number of Latin vowel letters in similar ways. Many languages, like English, make extensive use of combinations of vowel letters to represent various sounds. Other languages use vowel letters with modifications, e.g. Ä in Finnish, or add diacritical marks to vowels, such as accents or umlauts, to represent the variety of possible vowel sounds. Some languages have also constructed additional vowel letters by modifying the standard Latin vowels in other ways, such as æ or ø that are found in some of the Scandinavian languages. The International Phonetic Alphabet has a set of 28 symbols to represent the range of basic vowel qualities, and a further set of diacritics to denote variations from the basic vowel.

Written vowels in writing systems

 * Arabic: دَ دِ دُ دَ‌ا دَ‌ى دِ‌ي دُو
 * Devanagari: Independent vowels: अ आ इ ई उ ऊ ए ऐ ओ औ Dependent vowels: ा ि ी ु ू े ै ो ौ
 * Guaraní: oral: a e i o u y; nasal: ã ẽ ĩ õ ũ ỹ
 * Japanese: normal: あいうえお grammatical: へを
 * Korean: ㅏ ㅐ ㅑ ㅒ ㅓ ㅔ ㅕ ㅖ ㅗ ㅘ ㅙ ㅚ ㅛ ㅜ ㅝ ㅞ ㅟ ㅠ ㅡ ㅢ ㅣ
 * Latin: a e i o u y
 * Finnish: back: a u o; neutral: i e; front: ä y ö; long vowels doubled (aamu, uuma, etc.)
 * Estonian and Võro: a e i o u ü ä ö õ (y), half-long and over-long vowels doubled
 * Skolt Sami: u o õ å a, i e â ä (normal), u´ o´ õ´ å´ a´, i´ e´ â´ ä´ (centralized), long vowels doubled (lääij, nââ'ǩǩted, etc.).
 * Norwegian and Swedish: back ('hard'): a o u å; front ('soft'): e i y æ/ä ø/ö
 * Russian: non-iotating ('hard'): А О У Ы Э; iotating ('soft'): Я Ё Ю И Е