Japanese phonology

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This article deals with the phonology (the sound system) of Standard Japanese.

Consonants

	Bilabial	Alveolar	Postalveolar	Palatal	Velar	Uvular	Glottal
Stop	p  b	t  d			k  ɡ
Affricate		(t͡s)  (d͡z)	(t͡ɕ)  (d͡ʑ)
Nasal	m	n			(ŋ)	(ɴ)
Fricative	(ɸ)	s  z	(ɕ)  (ʑ)	(ç)			h
Flap			ɾ ~ ɺ
Approximant				j	ɰᵝ

Notes

• Voiceless stops /p t k/ are slightly aspirated: less aspirated than English stops, but more so than Spanish. /t d n/ are laminal denti-alveolar (that is, the blade of the tongue contacts the back of the upper teeth and the front part of the alveolar ridge) and /s z/ are laminal alveolar. The compressed velar is essentially a non-moraic version of the vowel /u/. It is not equivalent to a typical IPA [w], since it is pronounced with lip compression ([ɰᵝ]) rather than rounding.
• Consonants inside parentheses are allophones. Most notably, all taps and laterals are allophones of one underspecified phoneme. With the growing tendency of /h s z t d/ being pronounced distinctly (i.e., without the typical Japanese allophonic variation described below) in loanwords, [ɸ ɕ ʑ t͡s d͡z t͡ɕ d͡ʑ] are now tending to occur phonemically in recent loans. /ɴ/ may be considered an allophone of /n m/ in syllable-final position or a distinct phoneme.

See below for more in-detail descriptions of allophonic variation.

• Before /i/, /t d s z/ alveolo-palatal [tɕ dʑ ɕ ʑ] (often romanized ch j sh j) and before /u/ they are [ts dz] (often romanized ts dz/z).
• /z/ is pronounced [dz] by many speakers when word-initial or following the moraic nasal. It is [dʑ~ʑ] before /i/.
• /h/ is [ç] before /i/ and /j/ , and [ɸ] before /u/ (often romanized f) <phonos file="Ja-Fu.oga">listen</phonos>, coarticulated with the labial compression of that vowel.
• ɴ is a syllable-final moraic nasal with variable pronunciation depending on what follows.
• /r/ is an apical postalveolar flap undefined for laterality. That is, it is specified as neither a central nor a lateral flap, but may vary between the two. It is similar to the Korean r. To an English speaker's ears, its pronunciation varies between a flapped d ([ɾ], as in American English buddy) and a flapped l [ɺ], sounding most like d before /i/ and /j/ <phonos file="Ja-Ri.oga">listen</phonos>, most like l before /o/, and /a/ <phonos file="Ja-Ro.oga">listen</phonos>, and most like a retracted flap [ɾ̠] before /e/. It is occasionally realized as a trill [r], especially when conveying a vulgar nuance in speech. The phenomenon is called rolled tongue (巻き舌, makijita) in Japanese, and is usually transcribed by repeating katakana ru, e.g. ガルルルル for a dog's growl. It is sometimes transcribed with an l–ɾ ligature, lɾ.

Weakening

Non-coronal voiced stops /b, ɡ/ between vowels may be weakened to fricatives, especially in fast and/or casual speech:

		/b/ > bilabial fricative [β]:	/abareru/ > [aβaɾeɺɯᵝ] abareru 暴れる 'to behave violently'
		/ɡ/ > velar fricative [ɣ]:	/haɡe/ > [haɣe] hage はげ 'baldness'

However, /ɡ/ is further complicated by its variant realization as a velar nasal [ŋ]. Standard Japanese speakers can be categorized into 3 groups (A, B, C), which will be explained below. If a speaker pronounces a given word consistently with the allophone [ŋ] (i.e. a B-speaker), that speaker will never have [ɣ] as an allophone in that same word. If a speaker varies between [ŋ] and [ɡ] (i.e. an A-speaker) or is generally consistent in using [ɡ] (i.e. a C-speaker), then the velar fricative [ɣ] is always another possible allophone in fast speech.

/ɡ/ may be weakened to nasal [ŋ] when it occurs within words — this includes not only between vowels but also between a vowel and a consonant. There is a fair amount of variation between speakers, however. Some, such as Vance (1987), have suggested that the variation follows social class; others, such as Akamatsu (1997), suggest that the variation follows age and geographic location. The generalized situation is as follows.

At the beginning of words:

• all present-day standard Japanese speakers generally use the stop [ɡ] at the beginning of words:  /ɡaijuu/ > [ɡaijɯᵝɯᵝ] gaiyū 外遊 'overseas trip'   (but not *[ŋaijɯᵝɯᵝ])

In the middle of simple words (i.e. non-compounds):

• A. a majority of speakers uses either [ŋ] or [ɡ] in free variation:  /kaɡu/ > [kaŋɯᵝ] or [kaɡɯᵝ] kagu 家具 'furniture'
• B. a minority of speakers consistently uses [ŋ]:  /kaɡu/ > [kaŋɯᵝ]   (but not *[kaɡɯᵝ])
• C. most speakers in western Japan and a smaller minority of speakers in Kantō consistently use [ɡ]:  /kaɡu/ > [kaɡɯᵝ]   (but not *[kaŋɯᵝ])

In the middle of compound words morpheme-initially:

• B-speakers mentioned directly above consistently use [ɡ].

So, for some speakers the following two words are a minimal pair while for others they are homophonous:

• sengo 1,005 (せんご) 'one thousand five' = [seŋɡo] for B-speakers
• sengo 戦後 (せんご) 'postwar' = [seŋŋo] for B-speakers

To summarize using the example of hage はげ 'baldness':

• A-speakers: /haɡe/ > [haŋʲe] or [haɡʲe] or [haɣʲe]
• B-speakers: /haɡe/ > [haŋʲe]
• C-speakers: /haɡe/ > [haɡʲe] or [haɣʲe]

Palatalization and affrication

The palatals /i/ and /j/ palatalize the consonants preceding them:

		/m/ > palatalized [mʲ]:	/umi/ > [ɯᵝmʲi] umi 海 'sea'
		/ɡ/ > palatalized [ɡʲ]:	/ɡjoːza/ > [ɡʲjoːza] gyōza ぎょうざ 'fried dumpling'
		etc.

Exceptionally, /k/ and /ɡ/ before /e/ are also palatalized.

For coronal consonants, the palatalization goes further so that alveolopalatal consonants correspond with dental or alveolar consonants ([ta] 'field' vs. [tɕa] 'tea'):

		/s/ > alveolopalatal fricative [ɕ]:	/sio/ > [ɕi.o] shio 塩 'salt'
		/z/ > alveolopalatal [dʑ] or [ʑ]:	/zisiɴ/ > [dʑiɕĩɴ] jishin 地震 'earthquake'; /ɡozjuu/ > [ɡodʑɯᵝɯᵝ] ~ [ɡoʑɯᵝɯᵝ] gojuu 50 'fifty'
		/t/ > alveolopalatal affricate [tɕ]:	/tiziɴ/ > [tɕidʑĩɴ] ~ [tɕiʑĩɴ] chijin 知人 'acquaintance'

/i/ and /j/ also palatalize /h/ to a palatal fricative ([ç]): /hito/ > [çi̥to] hito 人 ('person')

Of the allophones of /z/, the affricate [dz] is most common, especially at the beginning of utterances and after /ɴ/ (or /n/, depending on the analysis), while fricative [z] may occur between vowels. Both sounds, however, are in free variation.

In the case of the /s/, /z/, and /t/, when followed by /j/, historically, the consonants were palatalized with /j/ merging into a single pronunciation. In modern Japanese, these are arguably separate phonemes, at least for the portion of the population that pronounces them distinctly in English borrowings.

		/sj/ > [ɕ] (Romanized as sh):	/sjaboɴ/ > /ɕaboɴ/ > [ɕabõɴ] shabon シャボン 'soap'
		/zj/ > [dʑ] or [ʑ] (Romanized as j):	/zjaɡaimo/ > /dʑaɡaimo/ > [dʑaŋaimo] jagaimo じゃがいも 'potato'
		/tj/ > [tɕ] (Romanized as ch):	/tja/ > /tɕa/ > [tɕa] cha 茶 'tea'
		/hj/ > [ç] (Romanized as hy):	/hjaku/ > /çakɯᵝ/ > [çakɯᵝ] hyaku 百 'hundred'

The vowel /u/ also affects consonants that it follows:

		/h/ > bilabial fricative [ɸ]:	/huta/ > [ɸɯ̥ᵝta] futa ふた 'lid'
		/t/ > dental affricate [ts]:	/tuɡi/ > [tsɯᵝŋi] tsugi 次 'next'

Although [ɸ] and [ts] occur before other vowels in loanwords (e.g. [ɸaito], 'fight'; [ɸjɯ̥ᵝːdʑoɴ], 'fusion'; [tsaitoɡaisu̥to], 'Zeitgeist'; [eɾitsiɴ], 'Yeltsin'), [ɸ] and [h] are distinguished before vowels except u（e.g. English fork v.s. hawk >[ɸoːkɯᵝ] fooku v.s [hoːkɯᵝ] hooku). *[hɯᵝ] is still not distinguished from [ɸɯᵝ] (e.g. English hood v.s. food > [ɸɯᵝːdo] fuudo). Similarly, *[si] and *[zi] do not occur even in loanwords so that English cinema becomes [ɕinema] shinema.

The moraic nasal /ɴ/

Some analyses of Japanese treat the moraic nasal as an archiphoneme /N/; however, other, less abstract approaches, take its uvular pronunciation as basic, or treat it as coronal /n/ appearing in the syllable coda. Even when the nasal coda is proposed as /N/, it is in a complementary distribution with the nasal onsets within a syllable. In any case, it undergoes a variety of assimilatory processes. Within words, it is variously:

• uvular [ɴ] at the end of utterances and in isolation.
• bilabial [m] before [p], [b] and [m]; this pronunciation is also sometimes found at the end of utterances and in isolation. Singers are taught to pronounce all final and prevocalic instances of this sound as [m], which reflects its historical derivation.
• dental [n] before coronals /d/, /t/, and /n/; never found utterance-finally.
• velar [ŋ] before [k] and [ɡ].
• some sort of nasalized vowel before vowels, approximants (/j/ and /w/), /r/, and fricatives (/s/, /z/, and /h/). Depending on context and speaker, the vowel's quality may closely match that of the preceding vowel or it may be more constricted in articulation. This pronunciation is also found utterance-finally.

Some speakers produce [n] before /z/, pronouncing them as [ndz], while others produce a nasalized vowel before /z/.

These assimilations occur beyond word boundaries.

Gemination

While Japanese features consonant gemination, there are some limitations in what can be geminated. Most saliently, voiced geminates are prohibited in native Japanese words. This can be seen with suffixation that would otherwise feature voiced geminates. For example, Japanese has a suffix, |ri| that contains what Kawahara (2006) calls a "floating mora" that triggers gemination in certain cases (e.g. |tap| +|ri| > [tappɯᵝɾi] ('a lot of'). When this would otherwise lead to a geminated voiced obstruent, a moraic nasal appears instead as a sort of "partial gemination" (e.g. |zabu| + |ri| > [zambɯᵝɾi] ('splashing').

However, voiced geminates do appear in loanwords. These loanwords can even come from languages, such as English, that do not feature gemination in the first place. For example, when an English word features a coda consonant followed by a lax vowel, it can be borrowed into Japanese featuring a geminate; gemination may also appear as a result of borrowing via written materials, where a word spelled with doubled letters leads to a geminated pronunciation. Because these loanwords can feature voiced geminates, Japanese now exhibits a voice distinction with geminates where it formerly did not:

suraggā スラッガー ('slugger') vs. surakkā ('slacker')

kiddo キッド ('kid') vs. kitto ('kit')

This distinction is not very rigorous. For example, when voiced obstruent geminates appear with another voiced obstruent they can undergo optional devoicing (e.g. doreddo ~ doretto, 'dreadlocks'). Kawahara (2006) attributes this to a less reliable distinction between voiced and voiceless geminates compared to the same distinction in non-geminated consonants, noting that speakers may have difficulty distinguishing them due to the partial devoicing of voiced geminates and their resistance to the weakening process mentioned above, both of which can make them sound like voiceless geminates.

There is some dispute about how gemination fits with Japanese phonotactics. One analysis, particularly popular among Japanese scholars, posits a special "mora phoneme" (モーラ 音素 Mōra onso) /Q/, which corresponds the sokuon ⟨っ⟩. However, not all scholars agree that the use of this "moraic obstruent" is the best analysis. In those approaches that incorporate the moraic obstruent, it is said to completely assimilate to the following obstruent, resulting in a geminate (that is, double) consonant. The assimilated /Q/ remains unreleased and thus the geminates are phonetically long consonants. /Q/ does not occur before vowels or nasal consonants. This can be seen as an archiphoneme in that it has no underlying place or manner of articulation, and instead manifests as several phonetic realizations depending on context, for example:

		[p̚] before [p]:	/niQpoN/ > [nʲip̚.põɴ] nippon 日本 'Japan'
		[s] before [s]:	/kaQseN/ > [kas.sẽɴ] kassen 合戦 'battle'
		[t̚] before [tɕ]:	/saQti/ > [sat̚.tɕi] satchi 察知 'inference'
		etc.

Another analysis of Japanese dispenses with /Q/ and other mora phonemes entirely. In such an approach, the words above are phonemicized as shown below:

		[p̚] before [p]:	/nippon/ > [nʲip̚.põɴ] nippon 日本 'Japan'
		[s] before [s]:	/kassen/ > [kas.sẽɴ] kassen 合戦 'battle'
		[t̚] before [tɕ]:	/satti/ > [sat̚.tɕi] satchi 察知 'inference'
		etc.

Gemination can of course also be transcribed with a length mark (e.g. [nʲipːõɴ], but this notation obscures mora boundaries.

/d, z/ neutralization

The contrast between /d/ and /z/ is neutralized before /u/ and /i/: [zɯᵝ, dʑi]. By convention, it is often assumed to be /z/, though some analyze it as /d/, the voiced counterpart to [ts]. The writing system preserves morphological distinctions, though spelling reform has eliminated historical distinctions except in cases where a mora is repeated once voiceless and once voiced, or where rendaku occurs in a compound word: つづく[続く] /tuduku/, いちづける[位置付ける /itidukeru/ from |iti+tukeru|,

Sandhi

Various forms of sandhi exist; the Japanese term for sandhi generally is ren'on (連音), while the Japanese form is referred to as renjō (連声). Most commonly, a terminal /n/ on one morpheme results in an /n/ (or /m/) being added to the start of the next morpheme, as in tennō (天皇, emperor), てん ＋ おう > てんのう (ten + ō = tennō). In some cases, such as this example, the sound change is used in writing as well, and is considered the usual pronunciation, though in other cases, such as abbreviating …-no-uchi (〜の家, …'s house) to 〜んち (-nchi) this is only done in speech, and considered informal. See 連声 (in Japanese) for further examples.

Vowels

The vowels of Standard Japanese on a vowel chart. Adapted from Okada (1991:94).

Vowel phonemes of Japanese

	Front	Central	Back
Close	i		ɯ
Mid	e		o
Open		a

• /ɯ/ is close centralized back compressed vowel [ɯᵝ] <phonos file="Ja-U.oga">listen</phonos>. It is pronounced with the lips compressed toward each other but neither rounded like [u] nor spread to the sides like [ɯ].
• /e, o/ are mid [e̞, o̞].
• /a/ is central [ä].

All of the Japanese vowels are pronounced as monophthongs. Except for /u/, the short vowels are similar to their Spanish or Italian counterparts.

Vowels have a phonemic length contrast (i.e. short vs. long). Compare contrasting pairs of words like ojisan /ozisaɴ/ 'uncle' vs. ojiisan /oziisaɴ/ 'grandfather', or tsuki /tuki/ 'moon' vs. tsūki /tuuki/ 'airflow'.

In most phonological analyses, all syllables with a short vowel as their rime are treated as occurring within the timeframe of one mora, or in other terms, one beat. According to traditional conventions, long vowels are described as a sequence of two identical vowels. For example, ojiisan will be rendered as /oziisaɴ/, not /oziːsaɴ/. Analysing long vowels in this manner is in accord with the traditions of Japanese linguistics and poetry, wherein long vowels are always considered separate moras.

Within words and phrases, Japanese allows long sequences of phonetic vowels without intervening consonants, pronounced with hiatus, although the pitch accent and slight rhythm breaks help track the timing when the vowels are identical. Sequences of two vowels within a single word are extremely common, occurring at the end of many i-type adjectives, for example, and having three or more vowels in sequence within a word also occurs, as in aoi 'blue/green'. In phrases, sequences with multiple o sounds are most common, due to the direct object particle を 'wo' (which comes after a word) being realized as o and the honorific prefix お〜 'o', which can occur in sequence, and may follow a word itself terminating in an o sound; these may be dropped in rapid speech. A fairly common construction exhibiting these is 「〜をお送りします」 ... (w)o o-okuri-shimasu 'humbly send ...'. More extreme examples follow:

/hoo.oo.ꜜo.ou/ [hòō.óò.ō.òɯ́ᵝ]	hōō o ou (鳳凰を追う)	'to chase Phoenix (Fenghuang)' (direct object)
/too.oo.oꜜ.oo.u/ [tòo.ōo.ó.òō.ɯ́ᵝ]	tōō o ōu (東欧を覆う)	'to cover Eastern Europe' (This artificial example would be unlikely in normal speech.)

Devoicing

In many dialects, the high vowels /i/ and /u/ become devoiced when between voiceless consonants. However, when a word contains more than one such environment, devoicing in adjacent syllables does not normally occur. Additionally, /i/ and /u/ are devoiced following a downstep and a voiceless consonant at the end of a prosodic unit.

		/kutuꜜ/ > [kɯ̥ᵝtsɯ́ᵝ]	kutsu 靴 'shoe'
		/aꜜtu/ > [átsɯ̥ᵝ]	atsu 圧 'pressure'
		/hikaɴ/ > [çi̥kãɴ́]	hikan 悲観 'pessimism'
		/hikaku/ > [çi̥kakɯ́ᵝ]	hikaku 比較 'comparison'
		/kisitu/ > [kʲi̥ɕitsɯᵝ]	kishitsu 気質 'temperament'

This devoicing is not restricted to only fast speech, though consecutive voicing may occur in fast speech.

To a lesser extent /o/ may devoice with the further requirement that there be two or more adjacent moras containing /o/:

/kokoꜜro/ > [ko̥kóɺò]

kokoro 心 'heart'

The common sentence-ending copula desu and polite suffix masu are typically pronounced [desu̥] and [masu̥].

Japanese speakers are usually not even aware of the difference of the voiced and devoiced pair. On the other hand, gender roles play a part in prolonging the terminal vowel: it is regarded as effeminate to prolong, particularly the terminal /u/ as in 'arimasu'. Some nonstandard varieties of Japanese can be recognized by their hyper-devoicing, while in some Western dialects and some registers of formal speech, every vowel is voiced.

Nasalization

Japanese vowels are slightly nasalized when adjacent to nasals /m, n/. Before the moraic nasal /ɴ/, vowels are heavily nasalized:

/seesaɴ/ > [seesãɴ́]

seisan 生産 'production'

Glottal stop insertion

At the beginning and end of utterances, Japanese vowels may be preceded and followed by a glottal stop [ʔ], respectively. This is demonstrated below with the following words (as pronounced in isolation):

		/eꜜɴ/ > [ẽ́ɴ̀] ~ [ʔẽ́ɴ̀]:	en 円 'yen'
		/kisiꜜ/ > [ki̥ɕíʔ]:	kishi 岸 'shore'
		/uꜜ/ > [ɯ́ᵝʔ] ~ [ʔɯ́ᵝʔ]:	u 鵜 'cormorant'

When an utterance-final word is uttered with emphasis, this glottal stop is plainly audible, and is often indicated in the writing system with a small letter tsu ⟨っ⟩ called a sokuon. This is also found in interjections like あっ and えっ. These words are likely to be romanized as ⟨a'⟩ and ⟨e'⟩, and rarely as ⟨at⟩ and ⟨et⟩

Phonotactics

	-a	-i/ʲi	-ɯ̥	-e	-o	-ʲa	-ʲu	-ʲo
'-	あ	い	う	え	お
k-	か	き	く	け	こ	きゃ	きゅ	きょ
g-	が	ぎ	ぐ	げ	ご	ぎゃ	ぎゅ	ぎょ
s-	さ		す	せ	そ
ɕ-	しゃ	し	しゅ		しょ
z-	ざ		ず	ぜ	ぞ
dʑ-	じゃ	じ	じゅ		じょ
t-	た			て	と
tɕ-	ちゃ	ち	ちゅ		ちょ
t͡s-			つ
d-	だ			で	ど
n-	な	に	ぬ	ね	の	にゃ	にゅ	にょ
h-	は			へ	ほ
ç-		ひ				ひゃ	ひゅ	ひょ
ɸ-			ふ
p-	ぱ	ぴ	ぷ	ぺ	ぽ	ぴゃ	ぴゅ	ぴょ
b-	ば	び	ぶ	べ	ぼ	びゃ	びゅ	びょ
m-	ま	み	む	め	も	みゃ	みゅ	みょ
j-	や		ゆ		よ
ɺ-	ら	り	る	れ	ろ	りゃ	りゅ	りょ
ɰᵝ-	わ	ゐ		ゑ	を

special mora	ɴ-	ん
	t̚ -	っ
	ː-	ー

Japanese words have traditionally been analysed as composed of moras; a distinct concept from that of syllables. Each mora occupies one rhythmic unit, i.e. it is perceived to have the same time value. A mora may be "regular" consisting of just a vowel (V) or a consonant and a vowel (CV), or may be one of two "special" moras, /N/ and /Q/. A glide /j/ may precede the vowel in "regular" moras (CjV). Some analyses posit a third "special" mora, /R/, the second part of a long vowel. In this table, the period represents a mora break, rather than the conventional syllable break.

Mora Type	Example	Japanese	moras per word
V	/o/	o 尾 'tail'	1-mora word
jV	/jo/	yo 世 'world'	1-mora word
CV	/ko/	ko 子 'child'	1-mora word
CjV	/kjo/	kyo 巨 'hugeness'	1-mora word
N	/N/   in /ko.N/ or /ko.n/	kon 紺 'deep blue'	2-mora word
Q	/Q/   in /ko.Q.ko/ or /ko.k.ko/	kokko 国庫 'national treasury'	3-mora word

^1 Traditionally, moras were divided into plain and palatal sets, the latter of which entail palatalization of the consonant element.

Consonantal moras are restricted from occurring word initially, though utterances starting with [n] are possible. Vowels may be long, and consonants may be geminate (doubled). In the analysis with archiphonemes, geminate consonants are the realization of the sequences /ɴn/, /ɴm/ and sequences of /Q/ followed by a voiceless obstruent, though some words are written with geminate voiced obstruents. In the analysis without archiphonemes, geminate clusters are simply two identical consonants, one after the other.

In English, stressed syllables in a word are pronounced louder, longer, and with higher pitch, while unstressed syllables are relatively shorter in duration. In Japanese, all moras are pronounced with equal length and loudness. Japanese is therefore said to be a mora-timed language.

Accent

Main article: Japanese pitch accent

Standard Japanese has a distinctive pitch accent system: a word can have one of its moras bearing an accent or not. An accented mora is pronounced with a relatively high tone and is followed by a drop in pitch. The various Japanese dialects have different accent patterns, and some exhibit more complex tonic systems.

Sound change

As an agglutinative language, Japanese has generally very regular pronunciation, with much simpler morphophonology than in fusional languages. Nevertheless, there are a number of prominent sound change phenomena, primarily in morpheme combination and in conjugation of verbs and adjectives. Phonemic changes are generally reflected in the spelling, though some non-phonemic changes are not reflected in spelling.

Sandhi

Rendaku

Main article: Rendaku

In Japanese, sandhi is prominently exhibited in rendaku – consonant mutation of the initial consonant of a morpheme from unvoiced to voiced in some contexts when it occurs in the middle of a word. This phonetic difference is reflected in the spelling via the addition of dakuten, as in ka, ga (か／が). In cases where this combines with the yotsugana mergers, notably ji, dzi (じ／ぢ) and zu, dzu (ず／づ) in standard Japanese, the resulting spelling is morphophonemic rather than purely phonemic.

Gemination

The other common sandhi in Japanese is conversion of つ or く (tsu, ku), and ち or き (chi, ki), and rarely ふ or ひ(fu, hi)as a trailing consonant to a geminate consonant when not word-final – orthographically, the sokuon っ, as this occurs particularly in the context of つ. So that

• 一(itsu) + 緒 (sho) = 一緒(issho)
• 学(gaku) + 校(kō) = 学校(gakkō)

Historically long vowels, especially "ō" in present japanese were all "f" foremerly so that

• 法(hafu *present hō) + 被(hi) = 法被(happi), instead of hōhi.
• 法(bofu *present bō) + 師(shi) = 法師(botchi), sometimes bōshi.
• 合(kafu *present gō) + 戦(sen) = 合戦(kassen), instead of gōsen
• 入(nifu *present nyū) + 声(shō) = 入声(nisshō), instead of nyūshō
• 十(jifu *present jū) + 戒(kai) = 十戒(jikkai) instead of jūkai

Renjō

Further information: 連声

Sandhi also occurs much less often in renjō (連声), where, most commonly, a terminal /N/ or /Q/ on one morpheme results in an /t/, /n/ (or /m/) being added to the start of the next morpheme, as in ten + ō = tennō (天皇、てん ＋ おう → てんのう).

First syllable ending with -N

• 「銀杏」(ginnan)　ぎん(gin) ＋ あん(an) → ぎんなん
• 「観音」(kannon)　くゎん(kwan) ＋ おむ (om) → くゎんのむ (kwannom)→ かんのん
• 「天皇」(tennō)　てん(ten) ＋ わう(wō) → てんなう → てんのう

First syllable ending with -M

• 「三位」(sammi)　さむ(sam) ＋ ゐ(wi) → さむみ → さんみ
• 「陰陽」(ommyō)　おむ(om) ＋ やう(yō) → おむみゃう → おんみょう

First syllable ending with -T

• 「雪隠」(setchin)　せつ(set) ＋ いん(in) → せっちん
• 「屈惑」(kuttaku)　くつ(kut) ＋ わく(waku) → くったく

Onbin

Further information: Euphonic changes (onbin)

Another prominent feature is onbin (音便, euphonic sound change), particularly historical sound changes.

In cases where this has occurred within a morpheme, the morpheme itself is still distinct but with a different sound, as in hōki (箒、ほうき, broom), which underwent two sound changes from earlier hahaki (ははき) → hauki (はうき) (onbin) → houki (ほうき) (historical vowel change) → hōki (ほうき) (long vowel, sound change not reflected in kana spelling).

However, certain forms are still recognizable as irregular morphology, particularly forms that occur in basic verb conjugation, as well as some compound words.

Verb conjugation

Further information: Onbin in verb conjugations

Polite adjective forms

Further information: Japanese grammar: Polite forms of adjectives

The polite adjective forms (used before the polite copula gozaru (ござる, be) and verb zonjiru (存じる, think, know)) exhibit a one-step or two-step sound change. Firstly, these use the continuative form, -ku (〜く), which exhibits onbin, dropping the k as -ku (〜く) → -u (〜う). Secondly, the vowel may combine with the preceding vowel, according to historical sound changes; if the resulting new sound is palatalized, meaning ゆ、よ (yu, yo), this combines with the preceding consonant, yielding a palatalized syllable.

This is most prominent in certain everyday terms that derive from an i-adjective ending in -ai changing to -ō (-ou), which is because these terms are abbreviations of polite phrases ending in gozaimasu, sometimes with a polite o- prefix. The terms are also used in their full form, with notable examples being:

• arigatō (有難う、ありがとう, Thank you), from arigatai (有難い、ありがたい, (I am) grateful).
• ohayō (お早う、おはよう, Good morning), from hayai (早い、はやい, (It is) early).
• omedetō (お目出度う、おめでとう, Congratulations), from (It is) auspicious (目出度い、めでたい).

Other transforms of this type are found in polite speech, such as oishiku (美味しく) → oishū (美味しゅう) and ōkiku (大きく) → ōkyū (大きゅう).

-hito

The morpheme hito (人（ひと）, person) (with rendaku -bito (〜びと)) has changed to uto (うと) or udo (うど), respectively, in a number of compounds. This in turn often combined with a historical vowel change, resulting in a pronunciation rather different from that of the components, as in nakōdo (仲人、なこうど, matchmaker) (see below). These include:

• otōto (弟、おとうと, younger brother), from otohito (弟人、おとひと) → otouto (おとうと) → otōto.
• imōto (妹、いもうと, younger sister), from imohito (妹人、いもひと) → imouto (いもうと) → imōto.
• shirōto (素人、しろうと, novice), from shirohito (白人、しろひと) → shirouto (しろうと) → shirōto.
• kurōto (玄人、くろうと, veteran), from 黒人 (くろひと, kurohito) → kurouto (くろうと) → kurōto.
• nakōdo (仲人、なこうど, matchmaker), from nakabito (仲人、なかびと) → nakaudo (なかうど) → nakoudo (なこうど) → nakōdo.
• karyūdo (狩人、かりゅうど, hunter), from karibito (狩人、かりびと) → kariudo (かりうど) → karyuudo (かりゅうど) → karyūdo.
• shūto (舅、しゅうと, stepfather), from shihito (舅、しひと) → shiuto (しうと) → shuuto (しゅうと) → shūto.

Fusion

In some cases morphemes have effectively fused and will not be recognizable as being composed of two separate morphemes.

Further reading

• (dissertation)