Speech sound in which air from the lungs passes through the mouth with minimal obstruction and without audible friction, like the i in fit. The word also refers to a letter representing such a sound (a, e, i, o, u, and sometimes y). In articulatory phonetics (see articulation), vowels are classified by tongue and lip position; for example, high vowels like the i in machine and the u in flute are both pronounced with the tongue arched high in the mouth, but in u the lips are also rounded. Single vowel sounds are monophthongs; two vowel sounds pronounced as one syllable, like the ou in round, are diphthongs.
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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 [ˈteɪ.bl̩] (the stroke under the l indicates that it is syllabic; the dot separates syllables), or the r in Serbian vrt [vr̩t] "garden".
We might note the conflict between the phonetic definition of 'vowel' (a sound produced with no constriction in the vocal tract) and the phonological definition (a sound that forms the peak of a syllable). The approximants [j] and [w] illustrate this conflict: both are produced without much of a constriction in the vocal tract (so phonetically they seem to be vowel-like), but they occur on the edge of syllables, such as at the beginning of the English words 'yes' and 'wet' (which suggests that phonologically they are consonants). The American linguist Kenneth Pike suggested the terms 'vocoid' for a phonetic vowel and 'vowel' for a phonological vowel, so using this terminology, [j] and [w] are classified as vocoids but not vowels.
The word vowel comes from the Latin word vocalis, meaning "speaking", because in most languages words and thus speech are not possible without vowels. Vowel is commonly used to mean both vowel sounds and the written symbols that represent them.
In spoken language, the articulatory features that distinguish different vowel sounds 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 the 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.
The International Phonetic Alphabet identifies seven different vowel heights:
True mid vowels do not contrast with both close-mid and open-mid in any language, and the letters are typically used for either close-mid or mid vowels.
Although English contrasts all six contrasting heights in its vowels, these are interdependent with differences in backness, and many are parts of diphthongs. It appears that some varieties of German have five contrasting vowel heights independently of length or other parameters. The Bavarian dialect of Amstetten has thirteen long vowels, reported to distinguish four heights (close, close-mid, mid, and near-open) each among the front unrounded, front rounded, and back rounded vowels, plus an open central vowel: . Otherwise, the usual limit on the number of contrasting vowel heights is four.
The parameter of vowel height appears to be the primary feature of vowels cross-linguistically in that all languages use height contrastively. No other parameter, such as front-back or rounded-unrounded (see 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.
Vowel backness is named for the position of the tongue during the articulation of a vowel relative to the back of the mouth. In front vowels, such as [i], the tongue is positioned forward in the mouth, whereas in back vowels, such as [u], the tongue is positioned towards the back of the mouth. However, vowels are defined as back or front not according to actual articulation, but according to the relative frequency of the second formant (F2). The higher the F2 value, the fronter the vowel; backness is thus inversely correlated to F2.
The International Phonetic Alphabet identifies five different degrees of vowel backness:
Although English has vowels at all five degrees of backness, there is no known language that distinguishes all five without additional differences in height or rounding.
Nonetheless, even in languages such as German and Vietnamese, there is usually some phonetic 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 and Norwegian are two of the few languages where this feature is contrastive, having 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 (pulled in and compressed; the margins of the lips approach each other) and exolabial rounding (pushed out and pursed; the insides of the lips approach each other). However, some 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).
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.
A stronger degree of pharyngealisation occurs 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 cords.
Note that the terms pharyngealized, epiglottalized, strident, and sphincteric are sometimes used interchangeably.
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 discourse about the English language, "tense and lax" are often used interchangeably with "long and short", respectively, because the features are concomitant in the common varieties of English. This cannot be applied to all English dialects or other languages.
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.
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 frequencies while close vowels have low F1 frequencies, as can be seen at right: The [i] and [u] have similar low first formants, whereas [ɑ] 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 [i] 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 an alternative measure of frontness is the difference between the first and second formants. For this reason, some people prefer to plot as F1 vs. F2 – F1. (This dimension is usually called 'backness' rather than 'frontness', but the term 'backness' can be counterintuitive when discussing formants.)
In the third edition of his textbook, Peter Ladefoged recommended use of plots of F1 against F2 – F1 to represent vowel quality. However, in the fourth edition, he changed to adopt a simple plot of F1 against F2, and this simple plot of F1 against F2 was maintained for the fifth (and final) edition of the book. Katrina Hayward compares the two types of plots and concludes that plotting of F1 against F2 – F1 "is not very satisfactory because of its effect on the placing of the central vowels", so she also recommends use of a simple plot of F1 against F2. In fact, this kind of plot of F1 against F2 has been used by analysts to show the quality of the vowels in a wide range of languages, including RP British English, the Queen's English, American English, Singapore English, Brunei English, North Frisian, Turkish Kabardian, and various indigenous Australian languages.
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.
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 for a few other languages, though not always as a phonemic distinction. Long vowels are written in the IPA with a triangular colon, which has two equilateral triangles pointing at each other in place of dots ([iː]). The IPA symbol for half-long vowels is the top half of this ([iˑ]). 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.
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 [ɪ], the vowel sound in boy is in most dialects a diphthong [ɔɪ], and the vowel sounds of, flower (BrE [aʊə] AmE [aʊɚ]) form a triphthong (disyllabic in the latter cases), although the particular qualities vary by dialect.
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 [flaʊə] AmE [flaʊɚ]) phonetically form a disyllabic triphthong, but are phonologically a sequence of a diphthong (represented by the letters 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 English. In the original Latin alphabet, there was no written distinction between V and U, and the letter represented the approximant [w] and the vowels [u] and [ʊ]. In Modern Welsh, the letter W represents these same sounds. Similarly, in Creek, the letter V stands for [ə]. 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 English spelling, the five letters A E I O and U can represent a variety of vowel sounds, while the letter Y frequently represents vowels (as in e.g. "gym" or "happy"); to an extremely limited extent, W can also represent a vowel (e.g. the borrowed word "cwm").
In most languages, vowels serve mainly to distinguish separate lexemes, rather than different inflectional forms of the same lexeme. For example, while English man becomes men in the plural, moon is not a different form of the same word. 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 inventories of vowels are larger than their inventories of consonants.
Written vowels
The name "vowel" is often used for the symbols that represent vowel sounds in a language's writing system, particularly if the language uses an alphabet. In writing systems based on the Latin alphabet, the letters A, E, I, O, U, W and Y are all used to represent vowels, although not all of these letters represent vowels in all languages (some of them, especially W and Y, are also used to represent approximants); in addition, extensions of the Latin alphabet have independent vowel letters such as Ä, Ö, Ü, Å, Æ, and Ø.
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, like umlauts, to vowels 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.
Use of vowels in languages
The importance of vowels in distinguishing one word from another varies from language to language. The alphabets used to write the Semitic languages, such as the Hebrew alphabet and the Arabic alphabet, do not ordinarily mark all the vowels, since they are frequently unnecessary in identifying a word. These alphabets are technically 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).See also
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