There are two complementary definitions of vowel, one
phonetic and the other
phonological. • In the
phonetic definition, a vowel is a sound, such as the
English "ah" or "oh" , produced with an open
vocal tract; it is median (the air escapes along the middle of the tongue), oral (at least some of the airflow must escape through the mouth),
frictionless and
continuant. There is no significant build-up of air pressure at any point above the
glottis. This contrasts with
consonants, such as the English "sh" , which have a constriction or closure at some point along the vocal tract. • In the phonological definition, a vowel is defined as
syllabic, the sound that forms the
peak of a syllable. A phonetically equivalent but non-syllabic sound is a
semivowel. In
oral languages, phonetic vowels normally form the peak (nucleus) of many or all syllables, whereas
consonants form the
onset and (in languages that have them)
coda. Some languages allow other sounds to form the nucleus of a syllable, such as the
syllabic (i.e., vocalic)
l in the English word
table (when not considered to have a weak vowel sound: ) or the syllabic
r in the
Serbo-Croatian word
vrt "garden". The phonetic definition of "vowel" (i.e. a sound produced with no constriction in the vocal tract) does not always match the phonological definition (i.e. a sound that forms the peak of a syllable). The
approximants and illustrate this: both are without much of a constriction in the vocal tract (so phonetically they seem to be vowel-like), but they occur at the onset of syllables (e.g. in "yet" and "wet") which suggests that phonologically they are consonants. A similar debate arises over whether a word like
bird in a
rhotic dialect has an
r-colored vowel or a syllabic consonant . The American linguist
Kenneth Pike (1943) suggested the terms "
vocoid" for a phonetic vowel and "vowel" for a phonological vowel; under this terminology, semivowels and are classified as vocoids but not vowels. However, Maddieson and Emmory (1985) demonstrated from a range of languages that semivowels are produced with a narrower constriction of the vocal tract than vowels, and so may be considered consonants on that basis. ==Articulation== The traditional view of vowel production, reflected for example in the terminology and presentation of the
International Phonetic Alphabet, is one of
articulatory features that determine a vowel's
quality as distinguishing it from other vowels.
Daniel Jones developed the
cardinal vowel system to describe vowels in terms of the features of tongue
height (vertical dimension), tongue
backness (horizontal dimension) and
roundedness (lip articulation). These three parameters are indicated in the schematic quadrilateral IPA
vowel diagram on the right. There are additional features of vowel quality, such as the
velum position (
nasality), type of
vocal fold vibration (
phonation), and
tongue root position. This conception of vowel articulation has been known to be inaccurate since 1928.
Peter Ladefoged said that "early phoneticians... thought they were describing the highest point of the tongue, but they were not. They were actually describing formant frequencies." (See below.) In the IPA
Handbook, the vowels are regarded as fixed articulatory reference points, with precise tongue positioning, while the remaining vowels are defined "so that the differences between each vowel and the next in the series are auditorily equal". As such, the
Handbook concedes: Nonetheless, the concept that vowel qualities are determined primarily by tongue position and lip rounding continues to be used in pedagogy, as it provides an intuitive explanation of how vowels are distinguished.
Height Theoretically, according to the traditional models,
vowel height refers to the vertical position of either the tongue or the jaw (depending on the model), relative to either the roof of the mouth or the aperture of the
jaw. There are two terms commonly applied to refer to two degrees of vowel height: in
close vowels, also known as
high vowels, such as and , the tongue is positioned close to the palate (i.e. high in the mouth), whereas in
open vowels, also known as
low vowels, such as , the jaw is open and the tongue is positioned low in the mouth. In
John Esling's usage, where
fronted vowels are distinguished in height by the position of the jaw rather than the tongue, only the terms 'open' and 'close' are used, as 'high' and 'low' refer to the position of the tongue. The
International Phonetic Alphabet defines letters for six degrees of vowel height for full vowels (plus the reduced mid vowel ), but it is extremely unusual for a language to distinguish this many degrees without other attributes. The IPA letters distinguish (sorted according to height, with the top-most one being the highest and the bottom-most being the lowest): •
close ( high): •
near-close ( near-high): •
close-mid ( high-mid): •
mid: •
open-mid ( low-mid): •
near-open ( near-low): •
open ( low): The letters are defined as close-mid but are commonly used for true
mid vowels. If more precision is required, true mid vowels may be written with a lowering or raising diacritic: or . The
Kensiu language, spoken in Malaysia and Thailand, is highly unusual in contrasting true mid vowels with both close-mid and open-mid vowels, without any additional parameters such as length, roundness or ATR. The front vowels, , along with open , make a six-way height distinction; this holds even for the nasal vowels. A few varieties of
German have been reported to have five contrastive vowel heights that are independent of length or other parameters. For example, the
Bavarian dialect of
Amstetten has thirteen long vowels, which have been analyzed as four vowel heights (close, close-mid, mid, open-mid) each among the front unrounded, front rounded, and back rounded vowels, along with an open vowel for a fifth height: . Apart from the aforementioned
Kensiu language, no other language is known to contrast more than four degrees of vowel height. The parameter of vowel height appears to be the primary cross-linguistic feature of vowels in that all
spoken languages that have been researched till now use height as a contrastive feature. No other parameter, even backness or rounding (see the two immediate sections below), is used in all languages. Some languages have
vertical vowel systems in which at least at a phonemic level, only height is used to distinguish vowels.
Backness front vowels with highest point indicated|class=skin-invert-image Within the traditional models,
vowel backness is named for the horizontal position of the tongue during the articulation of a vowel, relative to the back of the mouth. In front vowels, such as , the position of the tongue is more forward in the mouth, whereas in back vowels, such as , the tongue is positioned towards the back of the mouth. The
International Phonetic Alphabet defines five degrees of vowel backness (sorted according to backness, with the top-most one being the front-most back and the bottom-most being the back-most): •
front: •
near-front: •
central •
near-back: •
back: To them may be added front-central and back-central, corresponding to the vertical lines separating central from front and back vowel spaces in several IPA diagrams. However,
front-central and
back-central may also be used as terms synonymous with
near-front and
near-back. No language is known to contrast more than three degrees of backness independent of height, nor is there a language that contrasts front with near-front vowels nor back with near-back ones. Although some English dialects have vowels at five degrees of backness, there is no known language that distinguishes five degrees of backness without additional differences in height or rounding.
Roundedness Roundedness is named after the rounding of the lips in some vowels. Because lip rounding is easily visible, vowels may be commonly identified as rounded based on the articulation of the lips. In most languages, roundedness is a reinforcing feature of mid to high back vowels rather than a distinctive feature. Usually, the higher a back vowel, the more intense is the rounding. However, in some languages, roundedness is independent from backness, such as French and German (with front rounded vowels), most
Uralic languages (
Estonian has a rounding contrast for and front vowels),
Turkic languages (with a rounding distinction for front vowels and ), and
Vietnamese with back unrounded vowels. Nonetheless, even in those languages there is usually some phonetic correlation between rounding and backness: front rounded vowels tend to be more front-central than front, and back unrounded vowels tend to be more back-central than back. Thus, the placement of unrounded vowels to the left of rounded vowels on the IPA vowel chart is reflective of their position in formant space. Different kinds of
labialization are possible. In mid to high rounded back vowels the lips are generally protruded ("pursed") outward, a phenomenon known as
endolabial rounding because the insides of the lips are visible, whereas in mid to high rounded front vowels the lips are generally "compressed" with the margins of the lips pulled in and drawn towards each other, a phenomenon known as
exolabial rounding. However, not all languages follow that pattern.
Japanese , for example, is an exolabial (compressed) back vowel, and sounds quite different from an English endolabial .
Swedish and
Norwegian are the only two known languages in which the feature is contrastive; they have both exo- and endo-labial
close front vowels and
close central vowels, respectively. In many phonetic treatments, both are considered types of rounding, but some phoneticians do not believe that these are subsets of a single phenomenon and posit instead three independent features of
rounded (endolabial),
compressed (exolabial), and unrounded. The lip position of unrounded vowels may also be classified separately as
spread and
neutral (neither rounded nor spread). Others distinguish compressed rounded vowels, in which the corners of the mouth are drawn together, from compressed unrounded vowels, in which the lips are compressed but the corners remain apart as in spread vowels.
Front, raised and retracted The conception of the tongue moving in two directions, high–low and front–back, is not supported by articulatory evidence and does not clarify how articulation affects vowel quality. Vowels may instead be characterized by the three directions of movement of the tongue from its neutral position: front (forward), raised (upward and back), and retracted (downward and back). Front vowels ( and, to a lesser extent , etc.), can be secondarily qualified as close or open, as in the traditional conception, but this refers to jaw rather than tongue position. In addition, rather than there being a unitary category of back vowels, the regrouping posits
raised vowels, where the body of the tongue approaches the velum (], etc.), and
retracted vowels, where the root of the tongue approaches the pharynx (, etc.): •
front •
raised •
retracted Membership in these categories is scalar, with the mid-central vowels being marginal to any category.
Nasalization Nasalization occurs when air escapes through the nose. Vowels are often nasalized under the influence of neighbouring nasal consonants, as in
English hand .
Nasalized vowels, however, should not be confused with
nasal vowels. The latter refers to vowels that are distinct from their oral counterparts, as in
French vs. . 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.
Polish and
Portuguese also contrast nasal and oral vowels.
Phonation Voicing describes whether the
vocal cords are vibrating during the articulation of a vowel. Most languages have only voiced vowels, but several
Native American languages, such as
Cheyenne and
Totonac, have both voiced and devoiced vowels in complementary distribution. Vowels are devoiced in whispered speech. In Japanese and in
Quebec French, vowels that are between voiceless consonants are often devoiced.
Keres is disputed to have phonemic voiceless vowels but no language is confirmed to have them phonemically.
Modal voice,
creaky voice, and
breathy voice (murmured vowels) are
phonation types that are used contrastively in some languages. Often, they co-occur with
tone or stress distinctions; in the
Mon language, vowels pronounced in the high tone are also produced with creaky voice. In such cases, 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. The combination of phonetic cues (phonation, tone, stress) is known as
register or
register complex.
Tenseness Tenseness is used to describe the opposition of
tense vowels vs.
lax vowels. 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.
German), whereas the vowels of the other languages (e.g.
Spanish) cannot be described with respect to tenseness in any meaningful way. One may distinguish the English tense vs. lax vowels roughly, with its spelling. Tense vowels usually occur in words with the final
silent, as in
mate. Lax vowels occur in words without the silent , such as
mat. In
American English, lax vowels do not appear in stressed open syllables. In traditional grammar,
long vowels vs.
short vowels are more commonly used, compared to
tense and
lax. The two sets of terms are used interchangeably by some because the features are concomitant in some varieties of English. In most
Germanic languages, lax vowels can only occur in
closed syllables. Therefore, they are also known as
checked vowels, whereas the tense vowels are called
free vowels since they can occur in any kind of syllable.
Tongue root position Advanced tongue root (ATR) is a feature common across much of Africa, the
Pacific Northwest, and scattered other languages such as Modern
Mongolian. The contrast between advanced and retracted tongue root resembles the tense-lax contrast acoustically, but they are articulated differently. Those vowels involve noticeable tension in the vocal tract.
Secondary narrowings in the vocal tract Pharyngealized vowels occur in some languages like
Sedang and the
Tungusic languages. Pharyngealization is similar in articulation to retracted tongue root but is
acoustically distinct. A stronger degree of pharyngealization occurs in the
Northeast Caucasian languages and the
Khoisan languages. They might be called
epiglottalized since the primary constriction is at the tip of the epiglottis. The greatest degree of pharyngealization 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 cords. The terms
pharyngealized,
epiglottalized,
strident, and
sphincteric are sometimes used interchangeably.
Rhotic vowels Rhotic vowels are the "R-colored vowels" of American English and a few other languages.
Reduced vowels Some languages, such as English and Russian, have what are called 'reduced', 'weak' or 'obscure' vowels in some unstressed positions. These do not correspond one-to-one with the vowel sounds that occur in stressed position (so-called 'full' vowels), and they tend to be mid-centralized in comparison, as well as having reduced rounding or spreading. The IPA has long provided two letters for obscure vowels, mid and lower , neither of which are defined for rounding. Dialects of English may have up to four phonemic reduced vowels: , , and higher unrounded and rounded . (The non-IPA letters and may be used for the latter to avoid confusion with the clearly defined values of IPA letters like and , which are also seen, since the IPA only provides for two reduced vowels.) == Acoustics ==