Japanese phonology is the system of sounds used in the pronunciation of the Japanese language. Unless otherwise noted, this article describes the standard variety of Japanese based on the Tokyo dialect.
There is no overall consensus on the number of contrastive individual sounds (phonemes). Common approaches recognize at least 12 distinct consonants (as many as 21 in some analyses) and 5 distinct vowels, . Phonetic length is contrastive for both vowels and consonants, and the total length of Japanese words can be measured in a unit of timing called the mora (from Latin "delay"). Only limited types of consonant clusters are permitted. Japanese speech also has a pitch accent system in which the position or absence of a pitch drop may determine the meaning of a word: (), (), ().
Japanese phonology has been affected by the presence of several layers of vocabulary in the language. In addition to native Japanese vocabulary, Japanese has a large amount of Chinese-based vocabulary (used especially to form technical and learned words, playing a similar role to Latin-based vocabulary in English) and loanwords from other languages. Different layers of vocabulary allow different possible sound sequences (phonotactics).
Lexical strata
Many generalizations about the sound system of Japanese have exceptions when recent loanwords are taken into account. For example, the consonant generally does not occur at the start of native (Yamato) or Chinese-derived (Sino-Japanese) words, but it occurs freely in this position in mimetic and foreign words. Because of exceptions like this, discussions of Japanese phonology often refer to layers, or "strata," of vocabulary. The following four strata may be distinguished:
Yamato
Called or in Japanese, this category consists of inherited native vocabulary. Morphemes in this category show a number of restrictions on structure that may be violated by vocabulary in other layers.
Mimetic
Japanese possesses a variety of mimetic words that make use of sound symbolism to serve an expressive function. Like Yamato vocabulary, these words are also of native origin, and can be considered to belong to the same overarching group. However, words of this type show some phonological peculiarities that cause some theorists to regard them as a separate layer of Japanese vocabulary.
Sino-Japanese
Called in Japanese, words in this stratum originate from several waves of large-scale borrowing from Chinese that occurred from the 6th-14th centuries AD. They comprise 60% of dictionary entries and 20% of ordinary spoken Japanese, ranging from formal vocabulary to everyday words. Most Sino-Japanese words are composed of more than one Sino-Japanese morpheme. Sino-Japanese morphemes have a limited phonological shape: each has a length of at most two moras, which argue reflects a restriction in size to a single prosodic foot. These morphemes represent the Japanese phonetic adaptation of Middle Chinese monosyllabic morphemes, each generally represented in writing by a single Chinese character, taken into Japanese as kanji . Japanese writers also repurposed kanji to represent native vocabulary; as a result, there is a distinction between Sino-Japanese readings of kanji, called On'yomi, and native readings, called Kun'yomi.
The moraic nasal is relatively common in Sino-Japanese, and contact with Middle Chinese is often described as being responsible for the presence of in Japanese (starting from approximately 800 AD in Early Middle Japanese), although also came to exist in native Japanese words as a result of sound changes.
Foreign
Called in Japanese, this layer of vocabulary consists of non-Sino-Japanese words of foreign origin, mostly borrowed from Western languages after the 16th century; many of them entered the language in the 20th century. In words of this stratum, a number of consonant-vowel sequences that did not previously exist in Japanese are tolerated, which has led to the introduction of new spelling conventions and complicates the phonemic analysis of these consonant sounds in Japanese.
Consonants
{| class="wikitable" style="text-align: center;"
!
! Bilabial
! Alveolar
! Alveolo-<br />palatal
! Palatal
! Velar
! Uvular
! Glottal
!Special moras
|-
! Nasal
|
|
| ()
|
| ()
| ()
|
|
|-
! Plosive
|
|
|
|
|
|
|()
| rowspan="3" |
|-
! Affricate
|
| () ()
| () ()
|
|
|
|
|-
! Fricative
| () ()
|
| () ()
| ()
| () ()
|()
| ()
|-
! Liquid
|
| <!-- We use /r/ because realizations vary, just as do we at English phonology. -->
|
|
|
|
|
|
|-
! Semivowel
|
|
|
|
|
|
|
|
|}
Different linguists analyze the Japanese inventory of consonant phonemes in significantly different ways. recognizes only 12 underlying consonants (/m p b n t d s dz r k ɡ h/), whereas recognizes 16, equivalent to Smith's 12 plus the following 4 (/j w ts ɴ/), and recognizes 21, equivalent to Smith's 12 plus the following 9 (/j w ts tɕ (d)ʑ ɕ ɸ N Q/). Consonants inside parentheses in the table can be analyzed as allophones of other phonemes, at least in native words. In loanwords, sometimes occur phonemically.
In some analyses, the glides/semivowels are not interpreted as consonant phonemes. In non-loanword vocabulary, they generally occur only in the sequences and , which are sometimes analyzed as rising diphthongs rather than as consonant-vowel sequences. analyzes the glides as non-syllabic variants of the high vowel phonemes , arguing that the use of vs. may be predictable if both phonological and morphological context is taken into account.
Phonetic notes
Details of articulation
- are variously described as lamino-alveolar (), apico-alveolar () or apico-dental (), or simply dental or denti-alveolar.
- are lamino-alveolar .
- are lamino(dorso)-alveolopalatal . The affricates are sometimes transcribed broadly as (standing for prepalatal ). The palatalized allophone of before or is also lamino-alveolopalatal or prepalatal, and so can be transcribed as , or more broadly as . reports its place of articulation as dentoalveolar or alveolar.
- is traditionally described as a velar approximant or labialized velar approximant or something between the two, or as the semivocalic equivalent of with little to no rounding, while a 2020 real-time MRI study found it is better described as a bilabial approximant as there is less velar constriction in the consonant than in the vowel (vowels ought to have less constriction than consonants).
- is before and , and before , coarticulated with the labial compression of that vowel. When not preceded by a pause, it often may be breathy-voiced rather than voiceless .
- Realization of the liquid phoneme varies greatly depending on environment and dialect. The prototypical and most common pronunciation is an apical tap, either alveolar or postalveolar . Utterance-initially and after , the tap is typically articulated in such a way that the tip of the tongue is at first momentarily in light contact with the alveolar ridge before being released rapidly by airflow. This sound is described variably as a tap, a "variant of ", "a kind of weak plosive", and "an affricate with short friction, ". The apical alveolar or postalveolar lateral approximant is a common variant in all conditions, particularly utterance-initially and before . According to , utterance-initially and intervocalically (that is, except after ), the lateral variant is better described as a tap rather than an approximant. The retroflex lateral approximant is also found before . In Tokyo's Shitamachi dialect, the alveolar trill is a variant marked with vulgarity. Other reported variants include the alveolar approximant , the alveolar stop , the retroflex flap , the lateral fricative , and the retroflex stop .
Voice onset time
At the start of a word, the voiceless stops are slightly aspirated—less so than English stops, but more than those in Spanish. Word-medial seem to be unaspirated on average. Phonetic studies in the 1980s observed an effect of accent as well as word position, with longer voice onset time (greater aspiration) in accented syllables than in unaccented syllables.
A 2019 study of young adult speakers found that after a pause, word-initial may be pronounced as plosives with zero or low positive voice onset time (categorizable as voiceless unaspirated or "short-lag" plosives); while significantly less aspirated on average than word-initial , some overlap in voice onset time was observed. A secondary cue to the distinction between and in word-initial position is a pitch offset on the following vowel: vowels after word-initial (but not word-medial) start out with a higher pitch compared to vowels after , even when the latter are phonetically devoiced. Word-medial are normally fully voiced (or prevoiced), but may become non-plosives through lenition.
Lenition<span class="anchor" id="Weakening"></span>
The phonemes have weakened non-plosive pronunciations that can be broadly transcribed as voiced fricatives , although they may be realized instead as voiced approximants . There is no context where the non-plosive pronunciations are consistently used, but they occur most often between vowels:
:{| cellpadding="5"
| >
| >
|
|-
| >
| >
|
|-
| >
| >
|
|}
These weakened pronunciations can occur after a vowel in the middle of a word, or when a word starting with follows a vowel-final word with no intervening pause. found that, as with the pronunciation of as vs. , the use of plosive vs. non-plosive realizations of is closely correlated with the time available to a speaker to articulate the consonant, which is affected by speech rate as well as the identity of the preceding sound. All three show a high (over 90%) rate of plosive pronunciations after or after a pause; after , plosive pronunciations occur at high (over 80%) rates for and , but less frequently for , probably because word-medial after is often pronounced instead as a velar nasal (although the use of here may be declining for younger speakers). Across contexts, generally has a higher rate of plosive realizations than and .
Moraic consonants
Certain consonant sounds are called "moraic" because they count for a mora, a unit of timing or prosodic length. The phonemic analysis of moraic consonants is disputed. One approach, particularly popular among Japanese scholars, analyzes moraic consonants as the phonetic realization of special "mora phonemes" (): a mora nasal , called the hatsuon, and a mora obstruent consonant , called the sokuon. The pronunciation of these sounds varies depending on context: because of this, they may be analyzed as "placeless" phonemes with no phonologically specified place of articulation. A competing approach rejects the transcriptions and and the identification of moraic consonants as their own phonemes, treating them instead as the syllable-final realizations of other consonant phonemes (although some analysts prefer to avoid using the concept of syllables when discussing Japanese phonology).
Moraic nasal<span class="anchor" id="The_moraic_nasal_/%C9%B4/"></span>
The moraic nasal or mora nasal (hiragana , katakana , romanized as or ) can be interpreted as a syllable-final nasal consonant. Aside from certain marginal exceptions, it is found only after a vowel, which is phonetically nasalized in this context. It can be followed by a consonant, a vowel, or the end of a word:
:{| cellpadding="2"
|
|
| (hiragana: , three moras long)
|-
|
|
| (hiragana: , four moras long)
|-
|
|
| (hiragana: , two moras long)
|}
Its pronunciation varies depending on the sound that follows it (including across a word boundary).
- Before a plosive, affricate, nasal, or liquid, it is pronounced as a nasal consonant assimilated to the place of the following consonant:
:{| cellpadding="2"
| bilabial before
|
|
|-
| velar before
|
|
|-
| dorso-palatal before
|
|
|-
| lamino-alveolar before
|
|
|-
| lamino-alveolopalatal before
|
|
|-
| apico-alveolar or postalveolar before
| ,
| ,
|}
- Before a vowel, approximant , or voiceless fricative , it is a nasalized vowel or moraic semivowel that can be broadly transcribed as (its specific quality depends on the surrounding sounds). This pronunciation may also occur before the voiced fricatives , although more often, they are pronounced as affricates when preceded by the moraic nasal.
At the end of an utterance, the moraic nasal is pronounced as a nasal segment with a variable place of articulation and variable degree of constriction. Its pronunciation in this position is traditionally described and transcribed as uvular , sometimes with the qualification that it is, or approaches, velar after front vowels. Some descriptions state that it may have incomplete occlusion and can potentially be realized as a nasalized vowel, as in intervocalic position. Instrumental studies in the 2010s showed that there is considerable variability in its pronunciation and that it often involves a lip closure or constriction. A study of real-time MRI data collected between 2017 and 2019 found that the pronunciation of the moraic nasal in utterance-final position most often involves vocal tract closure with a tongue position that can range from uvular to alveolar: it is assimilated to the position of the preceding vowel (for example, uvular realizations were observed only after the back vowels ), but the range of overlap observed between similar vowel pairs suggests this assimilation is not a categorical allophonic rule, but a gradient phonetic process. 5% of the utterance-final samples of the moraic nasal were realized as nasalized vowels with no closure: in this case, appreciable tongue raising was observed only when the preceding vowel was .
There are a variety of competing phonemic analyses of the moraic nasal. It may be transcribed with the non-IPA symbol and analyzed as a "placeless" nasal. Some analysts do not categorize it as a phonological consonant. Alternatively, it may be analyzed as a uvular nasal , based on the traditional description of its pronunciation before a pause. It is sometimes analyzed as a syllable-final allophone of the coronal nasal consonant , but this requires treating syllable or mora boundaries as potentially distinctive, because there is a clear contrast in pronunciation between the moraic nasal and non-moraic before a vowel or before :
:{| cellpadding="5"
! colspan="2" style="text-align:left" | Moraic nasal
! colspan="2" style="text-align:left" | Non-moraic
|-
|
|
|
|
|-
|
|
|
|
|}
Alternatively, in an analysis that treats syllabification as distinctive, the moraic nasal can be interpreted as an archiphoneme (a contextual neutralization of otherwise contrastive phonemes), since there is no contrast in syllable-final position between and .
Thus, depending on the analysis, a word like , pronounced phonetically as , could be phonemically transcribed as , , or .
Moraic obstruent
There is a contrast between short (or singleton) and long (or geminate) consonant sounds. Compared to singleton consonants, geminate consonants have greater phonetic duration (realized for plosives and affricates in the form of a longer hold phase before the release of the consonant, and for fricatives in the form of a longer period of frication). A geminate can be analyzed phonologically as a syllable-final consonant followed by a syllable-initial consonant (although the hypothesized syllable boundary is not evident at the phonetic level) and can be transcribed phonetically as two occurrences of the same consonant phone in sequence: a geminate plosive or affricate is pronounced with just one release, so the first portion of such a geminate may be transcribed as an unreleased stop. As discussed above, geminate nasal consonants are normally analyzed as sequences of a moraic nasal followed by a non-moraic nasal, e.g. , = , . In the case of non-nasal consonants, gemination is mostly restricted by Japanese phonotactics to the voiceless obstruents /p t k s/ and their allophones. (However, other consonant phonemes can appear as geminates in special contexts, such as in loanwords.)
Geminate consonants can also be phonetically transcribed with a length mark, as in , but this notation obscures mora boundaries. uses the length marker to mark a moraic nasal, as , based on the fact that a moraic consonant by itself has the same prosodic weight as a consonant-vowel sequence: consequently, Vance transcribes Japanese geminates with two length markers, e.g. , , and refers to them as "extra-long" consonants, on the grounds that there is no acoustic boundary between two halves of a geminate. In the following transcriptions, geminates will be phonetically transcribed as two occurrences of the same consonant across a syllable boundary, the first being unreleased.
:{| cellpadding="5"
! colspan="3" style="text-align:left" | Singleton
! colspan="3" style="text-align:left" | Geminate
|-
|
|
| (, two moras long)
|
|
| (, three moras long)
|-
|
|
| (, three moras long)
|
|
| (, four moras long)
|-
|
|
| (, two moras long)
|
|
| (, three moras long)
|-
|}
A common phonemic analysis treats all geminate obstruents as sequences starting with the same consonant: a "mora obstruent", called the in Japanese, which can be phonemically transcribed with the non-IPA character . According to this analysis, , , are phonemically , , . This analysis seems to be supported by the intuition of native speakers and matches the use in kana spelling of a single symbol, a small version of the tsu sign (hiragana , katakana ) to write the first half of any geminate obstruent. Some analyses treat as an underlyingly placeless consonant.
Another approach dispenses with and treats geminate consonants as double consonant phonemes, that is, as sequences consisting of a consonant phoneme followed by itself. According to this analysis, , , are phonemically , , . Alternatively, since the contrast between different obstruent consonants such as , , is neutralized in syllable-final position, the first half of a geminate obstruent can be interpreted as an archiphoneme (just as the moraic nasal can be interpreted as an archiphoneme representing the neutralization of the contrast between the nasal consonants , in syllable-final position).
It has been suggested that the underlying phonemic representation of the sokuon might be a glottal stop . The sound is used in certain marginal forms that can be interpreted as containing not followed by another obstruent. For example, can be found at the end of an exclamation, or before a sonorant in forms with emphatic gemination, and is used as a written representation of in these contexts. This suggests that Japanese speakers identify as the default form of , or the form it takes when it is not possible for it to share its place and manner of articulation with a following obstruent. According to this analysis, , , are phonemically , , .
Even if it can be phonemically analyzed as , the sokuon is not always phonetically glottal. A study by used a video recording system and observed no glottal constriction during the pronunciation of Japanese geminate consonants. These results stand in conflict with the impressionistic descriptions of some authors, such as , who ascribes glottal tension to the first half of geminate consonants. An acoustic study by reported some evidence of creaky voice being more frequent for vowels following geminate consonants in Japanese (although only one of three measures of creakiness showed a significant difference). concludes that the role of glottal tension in Japanese geminates requires further research.
Voiced affricate vs. fricative
The distinction between the voiced fricatives (originally allophones of ) and the voiced affricates (originally allophones of ) is neutralized in Standard Japanese and in most (although not all) regional Japanese dialects. (Some dialects, e.g. Tosa, retain the distinctions between and and between and , while others distinguish only and but not and . Yet others merge all four, e.g. north Tōhoku.) argues that the difference between and may be marginally contrastive for some speakers, whereas denies that are ever distinguished in pronunciation from in adapted forms, regardless of whether the spellings and are used in writing.
The sequence (as opposed to either or ) also has some marginal use in loanwords. An example is . In many cases a variant adaptation with exists.
Alternations involving
Aside from arguments based on loanword phonology, there is also disagreement about the phonemic analysis of native Japanese forms. Some verbs can be analyzed as having an underlying stem that ends in either or ; these become or respectively before inflectional suffixes that start with :
{| cellpadding="5"
| [matanai] 'wait' (negative)
| vs.
| [matɕimasu] 'wait' (polite)
|-
| [kasanai] 'lend' (negative)
| vs.
| [kaɕimasu] 'lend' (polite)
|}
In addition, notes that in casual speech, or in verb forms may undergo coalescence with a following (marking the conditional), forming and respectively, as in for 'if (I) lend' and for 'if (I) win.' On the other hand, per , (more narrowly, ) can occur instead of for some speakers in contracted speech forms, such as for 'saying', for 'if one waits', and for 'if one speaks'; Vance notes these could be dismissed as non-phonemic rapid speech variants.
argues that alternations in verb forms do not prove is phonemically , citing (with ) vs. , , , etc. as evidence that a stem-final consonant is not always maintained without phonemic change throughout a verb's conjugated forms, and ~ '(must not) read' as evidence that palatalization produced by vowel coalescence can result in alternation between different consonant phonemes.
Competing phonemic analyses
There are several alternatives to the interpretation of as allophones of before or .
Some interpretations agree with the analysis of as an allophone of and as an allophone of (or ), but treat as the palatalized allophone of a voiceless coronal affricate phoneme (to clarify that it is analyzed as a single phoneme, some linguists phonemically transcribe this affricate as or with the non-IPA symbol ). In this sort of analysis, = .
Other interpretations treat as their own phonemes, while treating other palatalized consonants as allophones or clusters. The status of as phonemes rather than clusters ending in is argued to be supported by the stable use of the sequences in loanwords; in contrast, is somewhat unstable (it may be variably replaced with or ), and other consonant + sequences such as , are generally absent. (Aside from loanwords, also occur marginally in native vocabulary in certain exclamatory forms.)
It has alternatively been suggested that pairs like vs. could be analyzed as vs. . objects to analyses like on the basis that the sequence is otherwise forbidden in Japanese phonology.
Voiceless bilabial fricative
In core vocabulary, the voiceless bilabial fricative occurs only before . In this context, can be analyzed as an allophone of . Examples include () and (), which can be phonemically transcribed as , . Some descriptions of Japanese phonetics state that the initial sound of is not consistently produced as , but is sometimes a sound with weak or no bilabial friction that could be transcribed as (a voiceless approximant similar to the start of English "who").
In loanwords, can occur before other vowels or before . Examples include (), (), (), (), and (). Because of loanwords like these, the consonant is distinguished from before , as in the minimal pair () and () from English fork and hawk; likewise, is distinguished from before . Even in loanwords, is not distinguished from before : for example, English hood and food are both adopted as Japanese ().
The integration of , , , and into contemporary spoken Standard Japanese seems to have been completed at some point after the middle of the twentieth century, in the post-war period: before then, these sequences of sounds seem to have been commonly used only in educated pronunciation. Loanwords borrowed more recently than around 1890 fairly consistently show as an adaptation of foreign . Some older borrowed forms show adaptation of foreign to Japanese before a vowel other than , such as and .
Another old adaptation pattern replaced foreign with before a vowel other than , e.g. film > . Both of these replacement strategies are largely obsolete nowadays, although certain old adapted forms continue to be used, sometimes with specialized meanings compared to a variant pronunciation: for example, tends to be restricted in modern use to photographic films, whereas is used for other senses of "film" such as movie films.
Voiced bilabial fricative
Spellings with the kana have been used in narrow transcriptions into Japanese, in an attempt to render a voiced labiodental fricative, , in other languages, which most Japanese speakers find difficult. The actual pronunciation of a foreign "v sound" is normally not distinguished from a Japanese : for example, there is no meaningful phonological or phonetic difference in pronunciation between and , or between and considers an attempt at rendering to be a "foreignism," in other words, if an innovative Japanese speaker tries to pronounce it, they are treating it as part of a foreign word, rather than of a word that is fully integrated into Japanese lexicon. According to and , the foreign is realized in Japanese as a voiced bilabial fricative, , which already exists as an allophone of in the Yamato and Sino-Japanese strata, although it "seems to be much less fricative than the corresponding Castillan Spanish sound in lobo for instance". Thus, can be phonetically transcribed as . Irwin is non-committal on the phonemic status of . suggests a different realization, a "voiced labiodental spirant," thus , which is questioned by and rejected by . Depending on the source language, a foreign "v sound" can alternatively be rendered (in Hepburn romanization) as b, v or w.
Velar nasal onset
For some speakers, the velar nasal can occur as an onset in place of the voiced velar plosive in certain conditions. Onset , called , is generally restricted to word-internal position, where it may occur either after a vowel (as in ) or after a moraic nasal (as in ). It is debated whether onset constitutes a separate phoneme or an allophone of . They are written the same way in kana, and native speakers have the intuition that the two sounds belong to the same phoneme.
Speakers can be divided in three groups based on the extent to which they use in contexts where is not required: some consistently use , some never use , and some show variable use of versus (or ). Speakers who consistently use are a minority. The distribution of versus for these speakers mostly follows predictable rules (as described below): however, a number of complications and exceptions exist, and as a result, some linguists analyze as a distinct phoneme for consistent nasal speakers. The contrast has very low functional load, but it is possible to find or construct some pairs of words that are segmentally identical aside from the use of versus for consistent nasal speakers, such as () versus (). Another commonly cited pair is versus , although aside from the segmental difference in the consonant, these are prosodically distinct: the first is normally pronounced as two accent phrases, , whereas the second is pronounced as a single accent phrase (either or ).
Distribution of vs.
At the start of an independent word, all speakers use in almost all circumstances. However, postpositional particles, such as the subject marker , are pronounced with by consistent nasal speakers. In addition, a few words may be pronounced with even when they occur at the start of an utterance: examples include the conjunction and the word .
In the middle of a native morpheme, consistent nasal speakers always use . But in the middle of foreign-stratum morphemes, may be used even by consistent nasal speakers. It is also possible for foreign morphemes to be pronounced with medial : there is considerable variability, but this may be more common in older borrowings (such as , from Portuguese ) or in borrowings that contained in the source language (such as , from Portuguese ).
At the start of a morpheme in the middle of a word, either or may be possible, depending on the word. Only is possible after the honorific prefix (as in ) or at the start of a reduplicated mimetic morpheme (as in ). Consistent nasal speakers typically use at the start of the second morpheme of a bimorphemic Sino-Japanese word, or at the start of a morpheme that has undergone rendaku (that is, one that begins with when pronounced as an independent word). In cases where the second morpheme in a compound starts with when used independently, the compound might be pronounced with either or by consistent nasal speakers: factors such as the lexical stratum of the morpheme may play a role, but it seems difficult to establish precise rules predicting which pronunciation occurs in this context, and the pronunciation of some words varies even among consistent nasal speakers, such as .
The morpheme , is pronounced with when it is used as part of a compound numeral, as in (accented as ), although can potentially be pronounced as when it occurs non-initially in certain proper nouns or lexicalized compound words, such as (a male given name), (the name of a festival for children aged seven, five or three), or (a night of the full moon).
To summarize:
:{| class=wikitable style="border: none; background-color: transparent" | cellpadding="5"
| style="border-style: none" |
! in the middle of a morpheme
! at the start of a word
! rowspan=2 | at the start of a morpheme,<br>in the middle of a word
|-
| style="border-style: none" |
| style="background: #f9f9f9" |
| style="background: #f9f9f9" |
|-
! inconsistent speakers
| or or
| rowspan=3 | , but <em>not</em>
| rowspan=2 | sometimes , sometimes ~
|-
! consistent nasal speakers
|
|-
! consistent stop speakers
| or
| or
|}
Sociolinguistics of
The frequency of onset in Tokyo Japanese speech was falling as of 2008, and seems to have already been on the decline in 1940. Pronunciations with are generally less frequent for younger speakers, and even though the use of was traditionally prescribed as a feature of standard Japanese, pronunciations with seem in practice to have acquired a more prestigious status, as shown by studies that find higher rates of usage when speakers read words from a list. The frequency of also varies by region: it is rare in the southwestern Kansai dialects, but more common in the northeastern Tohoku dialects, with an intermediate frequency in the Kanto dialects (which includes the Tokyo dialect).
Vowels
thumb|upright=1.15|The vowels of Standard Japanese on a [[vowel chart. Adapted from .|class=skin-invert-image]]
{| class="wikitable" style="text-align: center;"
|+ class="nowrap" | Vowel phonemes of Japanese
!
! Front
! Central
! Back
|-
! Close
| || ||
|-
! Mid
| || ||
|-
! Open
| || ||
|}
- is central. shows a fronter quality, , while shows a backer quality, .
- are mid .
- is a close near-back vowel with the lips unrounded or compressed . When compressed, it is pronounced with the side portions of the lips in contact but with no salient protrusion. In conversational speech, compression may be weakened or completely dropped. It is centralized after and palatalized consonants (), and possibly also after . In contradiction to the preceding descriptions, characterize as rounded and propose that the transcription is more accurate than , while acknowledging the possibility of unrounding in fast speech. Based on visual recordings of Japanese speakers' lips, they conclude that is pronounced with lip protrusion (forward motion causing the lip corners to be brought closer together horizontally), in contrast to the spread lip position of a vowel like , or the vertical movement of the lips towards each other for the allophone of . They suggest that the perceptual impression of Japanese as an unrounded vowel could be caused partly by its fronted articulation, and partly by its protrusion being accompanied by less vertical lip closure compared to in other languages, resulting in a less rounded sound. Lip protrusion was also found to be greater for Japanese than for in a 2005 MRI study and in a 1997 study using x-ray microbeam kinematic data. A 2012 study using electromagnetic tracking observed Japanese to have greater lip protrusion in angry or sad emotional contexts than in emotionally neutral speech.
- All vowels are more centralized in prose than in individual words. The more careful the pronunciation, the less centralized the vowels are.
Long vowels and vowel sequences
All vowels display a length contrast: short vowels are phonemically distinct from long vowels:
:{| cellpadding="5"
|
|
|
|
|-
|
|
|
|
|-
|
|
|
|
|-
|
|
|
|
|-
|
|
|
|
|}
Long vowels are pronounced with around 2.5 or 3 times the phonetic duration of short vowels, but are considered to be two moras long at the phonological level. In normal speech, a "double vowel", that is, a sequence of two identical short vowels (for example, across morpheme boundaries), is pronounced the same way as a long vowel. However, in slow or formal speech, a sequence of two identical short vowels may be pronounced differently from an intrinsically long vowel:
:{| cellpadding="5"
|
|
|-
| ~
|
|-
|
|
|-
| ~
|
|}
In the above transcriptions, represents hiatus between two identical vowels at morpheme boundaries (which may occur when a speaker wishes to disambiguate an utterance). In the waveforms of carefully pronounced samples, a slight "dip in intensity" has been observed at the morpheme boundary between sato and oya in , but not in where such a boundary is not present. There is disagreement as to what causes this dip. describes it as "a diminution in loudness between the two vowels (sometimes accompanied by a slight glottal constriction) and a renewed pulse of expiration on the second." says that it is a "glottal stop", which the author considered a phoneme, and that "this phoneme also represents the glottal constriction associated with vowel rearticulation." says it can be "a pause or a light glottal stop". Both Martin and Labrune adopt the transcription [ˀ], a superscript glottal stop letter. Vance, following Martin, used the term "vowel rearticulation" and transcribed it as [ˀ] at first, but now adopts [*]. Vance's notion of "vowel rearticulation" has been criticized for citing Bloch's spurious phonetic description without proposing an alternative, such as whether palatal or labial glides can separate two identical vowels across morpheme boundaries, as in and . Given that the voicing of the vowels, facilitated by the vibration of the vocal folds, is not interrupted during hiatus, states that there is no complete glottal closure, questions whether there is any actual glottal narrowing at all, and notes that the articulation of the second vowel in involves slight labial narrowing. However, full glottal stops (with interrupted voicing) have been found to occur through acoustic analyses (previous descriptions by Bloch, Martin and Vance were impressionistic), albeit seldom in individual words and much less commonly even in slowly read sentences.
In fast speech, a sequence of two identical short vowels may fuse into one long vowel. This applies not only to and , but also to any two identical vowels straddling morpheme or word boundaries: , , , , .
A double vowel may bear pitch accent on either the first or second element, whereas an intrinsically long vowel can be accented only on its first mora. The distinction between double vowels and long vowels may be phonologically analyzed in various ways. One analysis interprets long vowels as ending in a special segment (or sometimes notated as ; in Japanese publications, the length mark is used) that adds a mora to the preceding vowel sound (a chroneme). Another analysis interprets long vowels as sequences of the same vowel phoneme twice, with double vowels distinguished by the presence of a "zero consonant" or empty onset between the vowels. A third approach also interprets long vowels as sequences of the same vowel phoneme twice, but treats the difference between long and double vowels as a matter of syllabification, with the long vowel consisting of the phonemes pronounced in one syllable, and the double vowel consisting of the same two phonemes split between two syllables.
Any pair of short vowels may occur in sequence (although only a subset of vowel sequences can be found within a morpheme in native or Sino-Japanese vocabulary). Sequences of three or more vowels also occur. Similar to the distinction between long vowels and double vowels, some analyses of Japanese phonology recognize a distinction between diphthongs (two different vowel phonemes pronounced in one syllable) and heterosyllabic vowel sequences; other analyses make no such distinction.
For certain verbs and adjectives with predictable accent locations, whether to phonologically analyze a sequence of two identical vowels as two separate vowels or a single continuous long vowel is a matter of convention, preference or accentual rules. For example, most accented verbs are predictably accented on the penultimate mora: thus is considered to have one long vowel if unaccented, as in , but two separate vowels if accented, as in . However, and are always accented on their antepenultimate mora, and this seemingly irregular location is attributed to a leftward accent shift to avoid accenting the special mora , which is almost always unaccentable and has been termed "deficient". Thus, these two verbs are said to have single long vowels, as in and .
Like accented verbs, most accented adjectives are also predictably accented on the penultimate mora, but for , some speakers accent the antepenultimate mora, pronouncing it as with a long vowel, while others accent the penultimate mora, pronouncing it as with two short sounds. Other forms of this verb, such as , are accented on the antepenultimate mora () in the conservative variety of Tokyo Japanese, and accented on the penultimate mora () in the innovating variety. On the other hand, while and are both unaccented and said to have one long vowel, is accented and has two vowels () because of an accentual rule that applies to all unaccented adjectives followed by the particle . conservatively has two vowels () and innovatingly has one long vowel () because of the different rule-based locations of the accent in the two varieties. Overall, in these particular cases, whether a double is treated as one long vowel or two vowels depends ad hoc on whether the second is accented.
As noted above, adjectival forms ending in are accented conservatively on the antepenultimate mora and innovatingly on the penultimate one. Yet for , the recommended patterns are conservatively on the preantepenultimate mora, as in , and innovatingly on the penultimate one, . In both cases, accentuating the antepenultimate mora is avoided and it maintains its status as the lengthening mora . The antepenultimate-accented pattern, , with two identical vowels rather than one long vowel, has not been widely recommended, although at least one source has claimed it is plausible. The antepenultimate mora of is similarly maintained as in two patterns: conservative and innovating . On the other hand, in , the two vowels result from a reduplication of the morpheme , therefore have a morpheme boundary between them, and the conservative pattern is simply .
forms historically can lose the consonant , which gives rise to long vowels by means of vowel fusion, as in → . These forms are found in non-Tokyo dialects, as well as in "super-polite" adjectival expressions with in Tokyo Japanese, as in . When is used this way, the result would be , with a potentially triply long vowel. Phonetically, a bilabial glide has been said to be added, which would yield , on account of the same glide existing in , but the actual production of that glide, which does not normally occur before the vowel , by native speakers, is inconclusive. As for and , 16th-century transcriptions such as and by European missionaries show that of the three 's, only the last two formed a long vowel. An Ōita dialect uses a different vowel quality for the last two vowels in these cases, roughly and , compared to the Tokyo and . The auxiliary (historically ) probably has the same effect in some verbs, such as