Editing Classical Japanese (section)

=== {{nihongo|Historical kana usage|歴史的仮名遣|rekishi-teki kana-zukai}} ===

[[Historical kana orthography|Historical kana usage]] is the system of [[kana]] (i.e., phonetic character) writing used in Japan before the post-war reforms. More specifically, it is the version of kana orthography standardized in the Meiji Period (since before that time kana usage was not standardized). It is, broadly speaking, based on the pronunciation of Japanese in the Heian Period, the time-frame in which Early Middle Japanese (on which the grammar of classical Japanese is based) was spoken. There are several differences between historical kana usage—which is also referred to as {{Nihongo|"old kana usage"|旧仮名遣|kyū kana-zukai}}—and the [[Modern kana usage|modern kana orthography]], called {{nihongo|"modern kana usage"|現代仮名遣|gendai kana-zukai}} or {{nihongo|"new kana usage"|新仮名遣|shin kana-zukai}}. Some of these differences apply primarily to [[Kanji#On'yomi (Sino-Japanese reading)|Sino-Japanese readings]] of Chinese characters, while others apply primarily to native Japanese words, and still others apply equally to both groups of words.

Broadly speaking, the differences are:

==== {{nihongo|H-Row|ハ行|ha-gyō}} rule ====

* Some morpheme-medial sounds currently written as {{nihongo2|わ/ワ}}, {{nihongo2|い/イ}}, {{nihongo2|う/ウ}}, {{nihongo2|え/エ}}, and {{nihongo2|お/オ}} (''wa'', ''i'', ''u'', ''e'', and ''o'') were written as {{nihongo2|は/ハ}}, {{nihongo2|ひ/ヒ}}, {{nihongo2|ふ/フ}}, {{nihongo2|へ/ヘ}}, and {{nihongo2|ほ/ホ}} (''ha'', ''hi'', ''fu'', ''he'', and ''ho''), respectively. This is because these sounds (as well as all sounds still written with {{nihongo2|は/ハ}}, {{nihongo2|ひ/ヒ}}, {{nihongo2|ふ/フ}}, {{nihongo2|へ/ヘ}}, and {{nihongo2|ほ/ホ}}) originally had initial consonant {{IPA|/p/}} in [[Old Japanese]], which then changed to {{IPA|/ɸ/}} in Early Middle Japanese, and then, in [[Late Middle Japanese]], split into one of five different phonemes depending on whether it occurred morpheme-initially or morpheme-medially, and then further depending on the following vowel. Morpheme-initially and before {{IPA|/a/}}, {{IPA|/e/}}, or {{IPA|/o/}}, it became {{IPA|/h/}}; before {{IPA|/i/}}, it became {{IPA|/ç/}}; and before {{IPA|/u/}}, it became {{IPA|/ɸ/}}; these three sounds are still written with {{nihongo2|は/ハ}}, {{nihongo2|ひ/ヒ}}, {{nihongo2|ふ/フ}}, {{nihongo2|へ/ヘ}}, and {{nihongo2|ほ/ホ}}. Morpheme-medially and before {{IPA|/a/}}, {{IPA|/i/}}, {{IPA|/e/}}, or {{IPA|/o/}}, it became {{IPA|/w/}}; before {{IPA|/u/}}, it lost its consonant. Finally, later on in the same period of the language the initial {{IPA|/w/}} was lost in all instances before {{IPA|/i/}}, {{IPA|/e/}}, and {{IPA|/o/}} (note that {{IPA|*/wu/}} never existed), leaving the current morpheme-medial pronunciations of {{IPA|/wa/}}, {{IPA|/i/}}, {{IPA|/u/}}, {{IPA|/e/}}, and {{IPA|/o/}}, but the spellings of {{IPA|/ha/}}, {{IPA|/hi/}}, {{IPA|/fu/}}, {{IPA|/he/}}, and {{IPA|/ho/}} (which, in this context, are probably better thought of as {{IPA|/pa/}}, {{IPA|/pi/}}, {{IPA|/pu/}}, {{IPA|/pe/}}, and {{IPA|/po/}}; or {{IPA|/fa/}}, {{IPA|/fi/}}, {{IPA|/fu/}}, {{IPA|/fe/}}, and {{IPA|/fo/}}). This rule primarily applies to native Japanese morphemes, although it is crucial to the mechanics of the long vowel rule that applies primarily to [[Sino-Japanese vocabulary|Sino-Japanese words]], which is elaborated upon below. The modern usage of {{nihongo2|は}} (''ha'') and {{nihongo2|へ}} (''he'') to represent grammatical particles pronounced as if written {{nihongo2|わ}} (''wa'') and {{nihongo2|え}} (''e''), respectively, is a holdover from this rule.

Some examples follow (old spellings are on the left, new spellings on the right; kana in parentheses represent the pronunciation of the preceding character):<ref>{{Cite web |title=ほのおとは何？ わかりやすく解説 Weblio辞書 |url=https://www.weblio.jp/content/%E3%81%BB%E3%81%AE%E3%81%8A |access-date=2022-06-11 |website=www.weblio.jp}}</ref><ref>{{Cite web |title=「仕合(しあわせ)」の意味や使い方 わかりやすく解説 Weblio辞書 |url=https://www.weblio.jp/content/%E4%BB%95%E5%90%88 |access-date=2022-06-11 |website=www.weblio.jp}}</ref><ref>{{Cite web |title=仕合はせの意味 – 古文辞書 – Weblio古語辞典 |url=https://kobun.weblio.jp/content/%E4%BB%95%E5%90%88%E3%81%AF%E3%81%9B |access-date=2022-06-11 |website=kobun.weblio.jp}}</ref><ref>{{Cite web |title=穂の意味 – 古文辞書 – Weblio古語辞典 |url=https://kobun.weblio.jp/content/%E7%A9%82 |access-date=2022-06-11 |website=kobun.weblio.jp}}</ref>
{{fs interlinear|indent=3|{幸せ (しあ'''は'''せ)} → {幸せ (しあ'''わ'''せ)}|shia'''ha'''se → shia'''wa'''se|c2= "happiness"|}}
{{fs interlinear|indent=3|{小さし (ち'''ひ'''さし)} → {小さい (ち'''い'''さい)}|chi'''hi'''sa-shi → chi'''i'''sa-i|c2="small" (the ''-shi'' ending is the classical conclusive form of modern {{nihongo2|小さい (ちいさい)}} ''chiisa-i'')|}}
{{fs interlinear|indent=3|{合'''ふ''' (あ'''ふ''')} → {合'''う''' (あ'''う''')}|a'''f-u''' → a-'''u'''|c2= "come together" (note that every quadrigrade verb that currently ends in {{nihongo2|う}} ''u'' once ended in {{nihongo2|ふ}} ''fu'')|}}
{{fs interlinear|indent=3|{前 (ま'''へ''')} → {前 (ま'''え''')}|ma'''he''' → ma'''e'''|c2= "front"|}}
{{fs interlinear|indent=3|{炎 (ほの'''ほ''')} → {炎 (ほの'''お''')}|hono'''ho''' → hon'''ō'''|c2= "flame"|}}

There are some exceptions to this sound change, although they are rare. They include {{nihongo2|母 (は'''は''')}} (''ha'''ha''''' "mother", expected form {{nihongo2|は'''わ'''}} ''ha'''wa'''''), {{nihongo2|頬 (ほ'''ほ''')}} (''ho'''ho''''' "cheek", expected form {{nihongo2|ほ'''お'''}} ''h'''ō'''''), {{nihongo2|家鴨 (あ'''ひ'''る)}} (''a'''hi'''ru'' "domestic duck", expected form {{nihongo2|あ'''い'''る}} ''a'''i'''ru''), and {{nihongo2|溢れる (あ'''ふ'''れる)}} (''a'''fu'''re-ru'' "overflow", expected form {{nihongo2|あ'''お'''れる}} ''a'''o'''re-ru'' or {{nihongo2|お'''う'''れる}} '''''ō'''re-ru''. Sometimes, as in the case of the first two exceptions, the sound change form exists, usually with a slightly different meaning ({{nihongo2|はわ}} ''hawa'' is a hyper-formal and very respectful term for mother) or is used in different contexts ({{nihongo2|ほお}} ''hō'' is generally used in isolation, while {{nihongo2|ほほ}} ''hoho'' is generally used in compounds). In other cases, as is true of the second two exceptions, the unchanged form is the only one that exists. In addition to these exceptions, some dialects may preserve these sounds as they were at any stage of the language.

==== {{nihongo|W-row|ワ行|wa-gyō}} rule ====

:''This section uses [[Nihon-shiki]] romanization for {{nihongo2|ゐ}}, {{nihongo2|ゑ}}, and {{nihongo2|を}}.''

* The obsolete characters {{nihongo2|ゐ/ヰ}} (''wi'') and {{nihongo2|ゑ/ヱ}} (''we'') are used, and the character {{nihongo2|を/ヲ}} (''wo'') is used in other words besides as the accusative or oblique case marker. This relates to the above rule, in that it reflects a pronunciation with initial {{IPA|/w/}} before {{IPA|/i/}}, {{IPA|/e/}}, and {{IPA|/o/}} that is no longer present in the modern language. This rule applies equally to native and Sino-Japanese words. The use of {{nihongo2|を}} (''wo'') to write the aforementioned grammatical particle, which is pronounced {{nihongo2|お}} (''o'') in modern Japanese (unless preceded by {{nihongo2|ん}} ''n'' or sometimes in song, although ''all'' morpheme-medial instances of {{IPA|/o/}}, whether originally {{nihongo2|お}}, {{nihongo2|を}}, or {{nihongo2|ほ}}, tend to become {{IPA|/wo/}} in song), is a holdover from this rule.

Some examples:

'''Native Japanese words'''
* {{nihongo2|居る ('''ゐ'''る) → 居る ('''い'''る)}} →  いる (only in kana) ('''''wi'''-ru'' → '''''i'''-ru'' "to be [animate objects]")
* {{nihongo2|聲 (こ'''ゑ''') → 声 (こ'''え''')}} (''ko'''we''''' → ''ko'''e''''' "voice") (notice that an old character is also involved in this example)
* {{nihongo2|男 ('''を'''とこ) → 男 ('''お'''とこ)}} ('''''wo'''toko'' → '''''o'''toko'' "male")
'''Sino-Japanese words'''
* {{nihongo2|役員 (やく'''ゐ'''ん) → 役員 (やく'''い'''ん)}} (''yaku'''wi'''n'' → ''yaku'''i'''n'' "officer")
* {{nihongo2|圓 ('''ゑ'''ん) → 円 ('''え'''ん)}} ('''''we'''n'' → '''''e'''n'' "Yen") (again, there is an old character used here)
* {{nihongo2|家屋 (か'''を'''く) → 家屋 (か'''お'''く)}} (''ka'''wo'''ku'' → ''ka'''o'''ku'' "house")

There are no known exceptions (besides the aforementioned ones regarding {{nihongo2|を}} ''wo'') in standard Japanese, and no dialects preserve the distinction between {{IPA|/wi/}} and {{IPA|/i/}}, {{IPA|/we/}} and {{IPA|/e/}}, and/or {{IPA|/wo/}} and {{IPA|/o/}}, but some of the [[Ryukyuan languages]] (which are also descended from [[Proto-Japonic]]) do.

==== {{nihongo|D-row|ダ行|da-gyō}} rule ====

:''This section uses Nihon-shiki romanization for {{nihongo2|じ}}, {{nihongo2|ず}}, {{nihongo2|ぢ}}, {{nihongo2|づ}}.''

* The characters {{nihongo2|ぢ/ヂ}} (''di'') and {{nihongo2|づ/ヅ}} (''du'') are used in places other than changes caused by [[Rendaku|sequential voicing]] ({{nihongo2|連濁}} ''Rendaku''), where in modern kana {{nihongo2|じ}} (''ji'') and {{nihongo2|ず}} (''zu''), respectively, would be used. Again, this represents a former phonetic distinction, namely between a sound {{IPA|/z/}} (in {{nihongo2|じ}} ''ji'' and {{nihongo2|ず}} ''zu'') and a sound {{IPA|/d/}} (in {{nihongo2|ぢ}} ''di'' and {{nihongo2|づ}} ''du''). This rule applies equally to native and Sino-Japanese words, as well as a few [[Gairaigo|loanwords]] ({{nihongo2|外来語}} ''Gairaigo'').

Some examples:

'''Native words'''
* {{nihongo2|紫陽花 (あ'''ぢ'''さゐ) → 紫陽花 (あ'''じ'''さい)}} (''a'''di'''sawi'' → ''a'''zi'''sai'' "hydrangea") (notice that this example also contains a change from {{nihongo2|ゐ}} ''wi'' to {{nihongo2|い}} ''i'')
* {{nihongo2|水 (み'''づ''') → 水 (み'''ず''')}} (''mi'''du''''' → ''mi'''zu''''' "water")
'''Sino-Japanese words'''
* {{nihongo2|解除 (かい'''ぢよ''') → 解除 (かい'''じょ''')}} (''kai'''diyo''''' → ''kai'''zyo''''' "release") (notice the use of Y-row rule, explained below)
* {{nihongo2|地圖 (ち'''づ''') → 地図 (ち'''ず''')}} (''chi'''du''''' → ''chi'''zu''''' "map") (notice again that an old character form is involved)
'''Loanwords'''
* {{nihongo2|ラ'''ヂ'''オ → ラ'''ジ'''オ}} (''ra'''di'''o'' → ''ra'''zi'''o'' "radio") (this one is especially notable because it is an exceedingly rare example of a sound change that occurs in a loanword from English)

There are no known exceptions in standard Japanese pronunciation, although there are many dialects (such as the [[Tosa dialect]]) that preserve the distinction between historical {{IPA|/z/}} and {{IPA|/d/}} in speech, usually by using {{IPA|/ʑi/}} and {{IPA|/zu/}} for historical {{IPA|/z/}} and {{IPA|/d͡ʑi/}} and {{IPA|/d͡zu/}} for historical {{IPA|/d/}} (see [[Yotsugana]]). In writing, the distinction is preserved in single morphemes in cases where a sequence {{nihongo2|ちぢ}} (''chidi'') or {{nihongo2|つづ}} (''tsudu'') was historically produced by rendaku (such as in {{nihongo2|縮む (ち'''ぢ'''む)}} ''chi'''di'''m-u'', "shorten", and {{nihongo2|続く (つ'''づ'''く)}} ''tsu'''du'''k-u'', "continue", pronounced as if {{nihongo2|ち'''じ'''む}} ''chi'''zi'''m-u'' and {{nihongo2|つ'''ず'''く}} ''tsu'''zu'''k-u'', respectively), or in compounds where a phonemic {{IPA|/ti/}} or {{IPA|/tu/}} has been voiced to {{IPA|/zi/}} or {{IPA|/zu/}} (such as in {{nihongo2|身近 (み'''ぢ'''か)}} ''mi-'''di'''ka'' "one's surroundings" and {{nihongo2|仮名遣 (かな'''づ'''かい)}} ''kana-'''du'''kai'' "kana usage", pronounced as if {{nihongo2|み'''じ'''か}} ''mi-'''zi'''ka'' and {{nihongo2|かな'''ず'''かい}} ''kana-'''zu'''kai'', respectively). This usage is a holdover from this rule.

==== {{nihongo|Y-row|ヤ行|ya-gyō}} rule ====

In modern Japanese, the small kana {{nihongo2|ゃ/ャ}}, {{nihongo2|ゅ/ュ}}, and {{nihongo2|ょ/ョ}} (''ya'', ''yu'', and ''yo'') are used to indicate [[palatalized consonant]]s ({{nihongo2|拗音}} ''Yōon'') when following an I-column ({{nihongo2|イ段}} ''I-dan'') kana of the K-, G-, N-, B-, P-, M-, or R-rows ({{nihongo2|カ～, ガ～, ナ～, バ～, パ～, マ～, ラ行}}; ''Ka-'', ''Ga-'', ''Na-'', ''Ba-'', ''Pa-'', ''Ma-'', ''Ra-gyō''). For example:

* {{nihongo2|客 ('''きゃ'''く)}} ('''''kya'''ku'' "guest")
* {{nihongo2|如実 ('''にょ'''じつ)}} ('''''nyo'''jitsu'' "reality")
* {{nihongo2|白檀 ('''びゃ'''くだん)}} ('''''bya'''kudan'' "sandalwood")
* {{nihongo2|'''ぴょ'''こ'''ぴょ'''こ}} ('''''pyo'''ko'''pyo'''ko'' "up and down")
* {{nihongo2|山脈 (さん'''みゃ'''く)}} (''san'''mya'''ku'' "mountain range")
* {{nihongo2|略 ('''りゃ'''く)}} ('''''rya'''ku'' "abbreviation")

When a small Y-row ({{nihongo2|ヤ行}} ''Ya-gyō'') kana follows an I-column kana of the S-, Z-, T-, D-, or H-rows ({{nihongo2|サ～, ザ～, タ～, ダ～, ハ行}}; ''Sa-'', ''Za-'', ''Ta-'', ''Da-'', ''Ha-gyō''), the preceding consonant is changed:

* {{nihongo2|食 ('''しょ'''く)}} ('''''sho'''ku'' "meal")
* {{nihongo2|樹立 ('''じゅ'''りつ)}} ('''''ju'''ritsu'' "establish")
* {{nihongo2|茶 ('''ちゃ''')}} ('''''cha''''' "tea")
* {{nihongo2|～中 ('''ぢゅう''')}} (''-'''jū''''' "throughout [suffix]") (note that, as noted above, {{nihongo2|ぢゃ}} ''ja'', {{nihongo2|ぢゅ}} ''ju'', and {{nihongo2|ぢょ}} ''jo'' only occur in modern Japanese writing when a sequence {{nihongo2|ちゃ}} ''cha'', {{nihongo2|ちゅ}} ''chu'', or {{nihongo2|ちょ}} ''cho'' is sequentially voiced, as in this example, and the pronunciation is identical to {{nihongo2|じゃ}} ''ja'', {{nihongo2|じゅ}} ''ju'', and {{nihongo2|じょ}} ''jo'') 
* {{nihongo2|百 ('''ひゃ'''く)}} ('''''hya'''ku'' "hundred") (note that the sequence {{IPA|/hj/}} is pronounced {{IPA|/ç/}} as noted above, but this difference is not reflected in any mainstream Japanese romanization system)

These three kana cannot follow A-row ({{nihongo2|ア行}} ''A-gyō'') or W-row ({{nihongo2|ワ行}} ''Wa-gyō'') kana in this way.

In historical kana, all of these examples are written with large kana {{nihongo2|や/ヤ}}, {{nihongo2|ゆ/ユ}}, and {{nihongo2|よ/ヨ}} (''ya'', ''yu'', and ''yo''). So the previous examples would be written:

* {{nihongo2|客 ('''きや'''く)}} (written '''''kiya'''ku'', but pronounced '''''kya'''ku'')
* {{nihongo2|如實 ('''によ'''じつ)}} (written '''''niyo'''jitsu'', but pronounced '''''nyo'''jitsu'') (note the presence of an old character form here)
* {{nihongo2|白檀 ('''びや'''くだん)}} (written '''''biya'''ku'', but pronounced '''''bya'''ku'')
* {{nihongo2|'''ぴよ'''こ'''ゝゝ'''ゝ}} (written '''''piyo'''ko'''piyo'''ko'', but pronounced '''''pyo'''ko'''pyo'''ko'') (again, multiple iteration marks are used here)
* {{nihongo2|山脈 (さん'''みや'''く)}} (written ''san'''miya'''ku'', but pronounced ''san'''mya'''ku'')
* {{nihongo2|略 ('''りや'''く)}} (written '''''riya'''ku'', but pronounced '''''rya'''ku'')
* {{nihongo2|食 ('''しよ'''く)}} (written '''''shiyo'''ku'', but pronounced '''''sho'''ku'')
* {{nihongo2|樹立 ('''じゆ'''りつ)}} (written '''''jiyu'''ritsu'', but pronounced '''''ju'''ritsu'')
* {{nihongo2|茶 ('''ちや''')}} (written '''''chiya''''', but pronounced '''''cha''''')
* {{nihongo2|～中 ('''ぢゆう''')}} (written ''-'''jiyū''''', but pronounced ''-'''jū''''')
* {{nihongo2|百 ('''ひや'''く)}} (written '''''hiya'''ku'', but pronounced '''''hya'''ku'')

This is the only historical kana rule that does not reflect a historical pronunciation. It is also one of only two rules (along with the geminate rule) that create ambiguity for the reader (excluding the exceptions listed above for the H-row rule). For instance, the aforementioned word {{nihongo2|客}} (''kyaku'') is not differentiated in historical kana from the word {{nihongo2|規約}} (''kiyaku'' "agreement") when written in historical kana: both are written {{nihongo2|きやく}} (''kiyaku'').

==== Geminate ({{nihongo2|促音}}, ''sokuon'') rule ====

The other use of small kana in modern Japanese is in the geminate consonant mark ({{nihongo2|促音}} ''Sokuon''), {{nihongo2|っ/ッ}}, which is a small version of {{nihongo2|つ/ツ}} (''tsu''). In native Japanese words, this symbol can be used before kana of the K-, S-, T-, and P-rows. For example,

* {{nihongo2|か'''っか'''}} (''ka'''kka''''' "burning hotly")
* {{nihongo2|真'''っ'''直ぐ (ま'''っす'''ぐ)}} (''ma'''ssu'''gu'' "straight")
* {{nihongo2|屹度 (き'''っと''')}} (''ki'''tto''''' "surely")
* {{nihongo2|葉'''っぱ''' (は'''っぱ''')}} (''ha'''ppa''''' "leaf")

Voiced geminates are generally prohibited by Japanese phonological rules, but they occur in a few loanwords (although they are sometimes pronounced by native speakers as if they were their voiceless counterparts). For example:

* {{nihongo2|スラ'''ッガー'''}} (''sura'''ggā''''' "slugger")
* {{nihongo2|キ'''ッド'''}} (''ki'''ddo''''' "kid")

Kana of the N- and M-rows can also be geminate, but they are preceded by {{nihongo2|ん}} (''n'') to indicate gemination instead.

Gemination can occur in Japanese for a variety of reasons. In native words, it occurs either when a historical long vowel elides, as in the aforementioned {{nihongo2|真っ直ぐ}} (''ma'''ssu'''gu'', originally {{nihongo2|ま'''あす'''ぐ}} ''ma'''asu'''gu''), or randomly, as in the aforementioned {{nihongo2|屹度}} (''ki'''tto''''', originally {{nihongo2|き'''と'''}} ''ki'''to'''''). These examples of the geminate consonant marker, along with those found in loanwords, are written with large {{nihongo2|つ}} (''tsu'') in historical kana. Therefore,

* {{nihongo2|か'''つか'''}} (written ''ka'''tsuka''''', but pronounced ''ka'''kka''''')
* {{nihongo2|真'''つ'''直ぐ (ま'''つす'''ぐ)}} (written ''ma'''tsusu'''gu'', but pronounced ''ma'''ssu'''gu'')
* {{nihongo2|屹度 (き'''つと''')}} (written ''ki'''tsuto''''', but pronounced ''ki'''tto''''')
* {{nihongo2|葉'''つぱ''' (は'''つぱ''')}} (written ''ha'''tsupa''''', but pronounced ''ha'''ppa''''')
* {{nihongo2|スラ'''ツガー'''}} (written ''sura'''tsugā''''', but pronounced ''sura'''ggā''''')
* {{nihongo2|キ'''ツド'''}} (written ''ki'''tsudo''''', but pronounced ''ki'''ddo''''')

In these cases, the historical usage is not reflecting any historical pronunciation. However, in Sino-Japanese words, geminate consonants are produced by different, more regular processes, and the historical usage for these words reflects historical pronunciations.

The most common way for geminates to be produced in Sino-Japanese words is by the elision of a vowel from the kana {{nihongo2|き}}, {{nihongo2|く}}, {{nihongo2|ち}}, or {{nihongo2|つ}} (''ki'', ''ku'', ''chi'', or ''tsu''). For example:

* {{nihongo2|適格 (て'''っか'''く)}} (''te'''kka'''ku'' "eligible", from ''teki'' + ''kaku'')
* {{nihongo2|学期 (が'''っき''')}} (''ga'''kki''''' "semester", from ''gaku'' + ''ki'')
* {{nihongo2|日程 (に'''って'''い)}} (''ni'''tte'''i'' "schedule", from ''nichi'' + ''tei'')
* {{nihongo2|雑誌 (ざ'''っし''')}} (''za'''sshi''''' "magazine", from ''zatsu'' + ''shi'')

In historical kana, where the geminate mark is used in the first, second, and fourth examples, a full-sized version of the '''''original''''' kana is used. However, in the third example, {{nihongo2|つ}} (''tsu'') is used, even though an {{IPA|/i/}} has been elided. The reason for this is that in Early Middle Japanese, when these sounds were borrowed from Middle Chinese, the Japanese language acquired a final {{IPA|/t/}} in the Sino-Japanese morphemes that currently end in {{nihongo2|ち}} (''chi'', {{IPA|/ti/}}) or {{nihongo2|つ}} (''tsu'', {{IPA|/tu/}}). Later on, these acquired two forms, one with {{IPA|/i/}} and one with {{IPA|/u/}} (although in syllables beginning with {{IPA|/ni/}}, one form usually begins with {{IPA|/zi/}}, as is the case with {{nihongo2|日}}). So the semantic difference between Sino-Japanese syllables ending in {{IPA|/ti/}} or {{IPA|/tu/}} is almost always trivial, and the historical pronunciation was identical, so they were not distinguished in writing. Therefore, the previous examples would be written:

* {{nihongo2|適格 (て'''きか'''く)}}  (''te'''kika'''ku'')
* {{nihongo2|學期 (が'''くき''')}} (''ga'''kuki''''') (note the old character form)
* {{nihongo2|日程 (に'''つて'''い)}} (''ni'''tsute'''i'')
* {{nihongo2|雜誌 (ざ'''つし''')}} (''za'''tsusi''''') (note the old character form)

Occasionally, gemination may also result from a loss of a vowel after {{nihongo2|ふ}} (''fu'', originally {{IPA|/pu/}}). These cases are complicated by the H-row rule, and perhaps because of that, are also written with {{nihongo2|つ}} in historical kana. For example,

* {{nihongo2|法師 (ほ'''っし''')}} (''ho'''sshi''''' "Buddhist priest", from ''hofu'' + ''shi'')

is written

* {{nihongo2|法師 (ほ'''つし''')}} (''ho'''tsushi''''')

in historical kana.

While this usage does reflect a historical pronunciation, it, like the Y-row rule, produces ambiguity. Furthermore, since these vowels are elided in some compounds but not others, this usage obscures the difference in a way that is essentially impossible to predict.

While there are a few other processes that can cause geminates in Sino-Japanese words, they all apply to N- and M-row kana, and are not written differently in historical and modern kana.

==== Labialized consonant ({{nihongo2|合拗音}}, ''gōyōon'') rule ====

Starting in Early Middle Japanese, as more and more Chinese characters were borrowed into Japanese, the language acquired consonants fronted with glides. Those fronted with the palatal glide are described in the Y-row rule, but Early Middle Japanese also introduced consonants fronted with labial glides (i.e., CwV). These were far more limited in range than their palatal counterparts, however, affecting only the K- and G- rows. instead of {{IPA|/a/}}, {{IPA|/u/}}, and {{IPA|/o/}} for the vowels of onset, like the palatal glides, the vowels of onset for the labial glides were {{IPA|/a/}}, {{IPA|/i/}}, and {{IPA|/e/}}, and used the kana {{nihongo2|わ}}, {{nihongo2|ゐ}}, and {{nihongo2|ゑ}} (''wa'', ''wi'', and ''we''). Finally, while the palatal glides are written with an I-column kana, the labial glides are written with a U-column ({{nihongo2|ウ段}} ''U-dan'') kana. However, when historical kana was standardized in the Meiji Period, only the syllables with historical {{IPA|/wa/}} were indicated. Nevertheless, some classical texts may indicate the other differences, and some resources will refer to them, so it is useful to be familiar with them. This rule applies exclusively to Sino-Japanese words. Some examples:

'''{{nihongo2|くわ}} (written ''kuwa'', but pronounced ''kwa'') and {{nihongo2|ぐわ}} (written ''guwa'', but pronounced ''gwa'') (indicated in standard historical kana)'''
* {{nihongo2|菓子 ('''くわ'''し) → 菓子 ('''か'''し)}} ('''''kwa'''shi'' → '''''ka'''shi'' "sweets")
* {{nihongo2|元旦 ('''ぐわ'''んたん) → 元旦 ('''が'''んたん)}} ('''''gwa'''ntan'' → '''''ga'''ntan'' "New Year's Day")
'''{{nihongo2|くゐ}} (written ''kuwi'', but pronounced ''kwi''), {{nihongo2|ぐゐ}} (written ''guwi'', but pronounced ''gwi''), {{nihongo2|くゑ}} (written ''kuwe'', but pronounced ''kwe''), and {{nihongo2|ぐゑ}} (written ''guwe'' but pronounced ''gwe'') (not indicated in standard historical kana)'''
* {{nihongo2|歸省 ('''くゐ'''せい) → 帰省 ('''き'''せい)}} ('''''kwi'''sei'' → '''''ki'''sei'' "homecoming") (note the old character form)
* {{nihongo2|僞善 ('''ぐゐ'''ぜん) → 偽善 ('''ぎ'''ぜん)}} ('''''gwi'''zen'' → '''''gi'''zen'' "hypocrisy") (note the old character form)
* {{nihongo2|番犬 (ばん'''くゑ'''ん) → 番犬 (ばん'''け'''ん)}} (''ban'''kwe'''n'' → ''ban'''ke'''n'' "watchdog")
* {{nihongo2|同月 (どう'''ぐゑ'''つ) → 同月 (どう'''げ'''つ)}} (''dou'''gwe'''tsu'' → ''dou'''ge'''tsu'' "same month")

[[Labialized consonant]]s sometimes occur in modern loanwords, and they are generally dealt with in one of two ways. Firstly, the labialized consonant may be changed from a sequence {{IPA|/CwV/}} to a sequence {{IPA|/CuwV/}}, both in writing and in speech. For example,

* {{nihongo2|'''クイ'''ック}} ('''''kui'''kku'' "quick", from English "quick" with original {{IPA|/kw/}})

In other cases, they may be indicated with a U-column kana followed by a small A-row kana, indicating a labialized consonant. For example,

* {{nihongo2|'''クィー'''ン}} ('''''kwī'''n'' "queen", from English "queen" with original {{IPA|/kw/}})

However, in these cases, an alternative version with large A-row kana generally exists (as it does in this case), indicating a monophthong pronunciation, and many speakers use the monophthong pronunciation regardless of how it is written.

There are no known exceptions to this rule, but some dialects (such as the [[Kagoshima dialect]]) preserve the distinction.

==== Long vowel ({{nihongo2|長音}}, ''chōon'') rule ====

{{Empty section|date=June 2024}}

==== Palatalized long vowel ({{nihongo2|開拗長音}}, ''kaiyōchōon'') rule ====

{{Empty section|date=June 2024}}

==== Classical auxiliary verb {{nihongo2|む}} (''mu'') rule ====

Modern Japanese has the moraic nasal {{nihongo2|ん}} (''n''), which can represent a variety of sounds depending on what sounds come before and after it. Syllable final nasals are believed by many scholars to have existed in Proto-Japonic, but all agree that they were lost by the time of Old Japanese. They first re-appeared in Early Middle Japanese, with the introduction of [[Middle Chinese]] loanwords ending in ''-n'' and ''-m''. Therefore, the majority of occurrences of {{nihongo2|ん}} (''n'') in modern Japanese occur in Sino-Japanese vocabulary. Originally, syllabic ''n'' and ''m'' were phonemically and phonologically distinct, although the distinction was never written down, and was lost by [[Early Modern Japanese]]. For example,

* {{nihongo2|漢字 (か'''ん'''じ)}} (''ka'''n'''zi'', from Middle Chinese {{IPA|hɑ'''n'''ᴴd͡zɨᴴ}})
* {{nihongo2|音樂 (お'''ん'''がく)}} (''o'''n'''gaku'', from Middle Chinese {{IPA|''ʔiɪ'''m'''ŋˠʌk̚''}}; originally pronounced ''o'''m'''gaku'') (note the old character form)

However, some native Japanese words also have {{nihongo2|ん}} (''n''). This happens exceedingly rarely, and usually results from sound elision. An exhaustive list of every example out of all [[Jōyō kanji|regular-use characters]] with the syllabic nasal in their native Japanese readings numbers only 13 characters (0.61% of the regular-use set) giving rise to 14 readings. They are

'''From the elision of a vowel following /m/ or /n/'''
* {{nihongo2|何 (な'''ん''')}} (''na'''n''''' "what"), from {{nihongo2|な'''に'''}} (''na'''ni''''' "what")
* {{nihongo2|女 (を'''ん'''な)}} (''wo'''n'''na'' "woman"), originally pronounced ''wo'''m'''na''; from {{nihongo2|を'''み'''な}} (''wo'''mi'''na'' "woman") (in modern orthography, {{nihongo2|'''お'''んな}} '''''o'''nna'' and {{nihongo2|'''お'''みな}} '''''o'''mina'')
* {{nihongo2|懇ろ (ね'''ん'''ごろ)}} (''ne'''n'''goro'' "courteous"), originally pronounced ''ne'''m'''koro''; from {{nihongo2|ね'''も'''ころ}} (''ne'''mo'''koro'' "courteous")
* {{nihongo2|神 (か'''ん''')}} (''ka'''n''''' "god" in some compounds), originally pronounced ''ka'''m'''''; from {{nihongo2|か'''み'''}} (''ka'''mi''''' "god") (in modern orthography, {{nihongo2|神}}, using a new character form)
* {{nihongo2|考ふ (か'''ん'''がふ)}} (''ka'''n'''gaf-u'' "consider"), from {{nihongo2|か'''む'''がふ}} (''ka'''mu'''gaf-u'' "consider"); note that these are the classical versions of the modern verbs {{nihongo2|考へる (かんがへる)}} (''kangahe-ru'') and {{nihongo2|考へる (かうがへる)}} (''kaugahe-ru''), respectively (in modern orthography, {{nihongo2|かんが'''う'''}} ''kanga'''u''''', {{nihongo2|'''こう'''が'''う'''}} '''''kō'''ga-'''u''''', {{nihongo2|かんが'''え'''る}} ''kanga'''e'''-ru'', and {{nihongo2|'''こう'''が'''え'''る}} '''''kō'''ga'''e'''-ru'', respectively)
'''From the elision of a full mora'''
* {{nihongo2|冠 (か'''ん'''むり)}} (''ka'''n'''muri'' "crown"), from {{nihongo2|か'''う'''ぶり}} (''ka'''u'''buri'' "rank"); note also the sound change from {{IPA|/b/}} to {{IPA|/m/}} (in modern orthography, {{nihongo2|'''かう'''ぶり}} '''''kau'''buri'' is {{nihongo2|'''こう'''ぶり}} '''''kō'''buri'')
* {{nihongo2|問 (と'''ん''')}} (''to'''n''''' "wholesale" in the compound {{nihongo2|問屋}} ''to'''n''''ya'' "wholesale store"), from {{nihongo2|と'''ひ'''}} (''to'''hi''''' "query") (in modern orthography, {{nihongo2|と'''ひ'''}} ''to'''hi''''' is {{nihongo2|と'''い'''}} ''to'''i''''')
* {{nihongo2|盛'''ん''' (さか'''ん''')}} (''saka'''n''''' "prosperous"), from {{nihongo2|さか'''り'''}} (''saka'''ri''''' "one's best days")
* {{nihongo2|芳し (か'''ん'''ばし)}} (''ka'''n'''ba-shi'' "fragrant"), from {{nihongo2|か'''ぐ'''はし}} (''ka'''gu'''ha-si'' "fragrant"); note also the sequential voicing of {{IPA|/h/}} to {{IPA|/b/}}, and that these are the classical forms of the adjectives {{nihongo2|芳しい (かんばしい)}} (''kanba-shii'') and {{nihongo2|芳しい (かぐはしい)}} (''kaguha-shii'') (in modern orthography, {{nihongo2|かぐ'''は'''し}} ''kagu'''ha'''-shi'' is {{nihongo2|かぐ'''わ'''し}} ''kagu'''wa'''-shi'' and {{nihongo2|かぐ'''は'''しい}} ''kagu'''ha'''-shii'' is {{nihongo2|かぐ'''わ'''しい}} ''kagu'''wa'''-shii'')
'''From the preservation of an Old Japanese pre-nasalized consonant in a modern Japanese word'''
* {{nihongo2|鑑みる (か'''ん'''がみる)}} (''ka'''n'''gami-ru'' "learn from"), from {{nihongo2|か'''ゞ'''みる}} (''ka'''ga'''mi-ru'' "learn from") (in modern orthography, {{nihongo2|か'''ゞ'''みる}} ''ka'''ga'''mi-ru'' is {{nihongo2|か'''が'''みる}} ''ka'''ga'''mi-ru'', without iteration marks)
* {{nihongo2|丼}} ({{nihongo2|ど'''ん'''ぶり}}) (''do'''n'''buri'' "porcelain bowl"), from {{nihongo2|ど'''ぶ'''り}} (''do'''bu'''ri'' "[sound symbolism for something big and soft plopping down]")
'''From abbreviation of another pronunciation on this list'''
* {{nihongo2|丼}} ({{nihongo2|ど'''ん'''}}) (''do'''n''''' "porcelain bowl"), originally pronounced ''do'''m'''''; from aforementioned {{nihongo2|ど'''ん'''ぶり}} (''do'''n'''buri'' "porcelain bowl")
'''From multiple processes'''
* {{nihongo2|御 (お'''ん''')}} (''o'''n''' "[honorific prefix]"), originally pronounced ''o'''m'''''; from {{nihongo2|大 (おほ)}} (''oho'' "great") + {{nihongo2|御 ('''み''')}} ('''''mi''''' "august"), which became {{nihongo2|大御 (おほ'''み''')}} (''oho'''mi''''' "august"), and then {{nihongo2|御 (おほ'''ん''')}} by elision of {{IPA|/i/}} after {{IPA|/m/}}, and finally {{nihongo2|御 (お'''ん''')}} (''o'''n''') by elision of the full mora {{IPA|/ho/}}; note the use of the character {{nihongo2|御}} instead of {{nihongo2|大御}} is ateji (in modern orthography, {{nihongo2|お'''ほ'''}} '''''oho''''' is {{nihongo2|お'''お'''}} '''''ō''''', {{nihongo2|お'''ほ'''み}} '''''oho'''mi'' is {{nihongo2|お'''お'''み}} '''''ō'''mi'', and {{nihongo2|お'''ほ'''ん}} '''''oho'''n'' is お'''お'''ん '''''ō'''n'')
'''From some semantic (rather than phonetic) process'''
* {{nihongo2|四 (よ'''ん''')}} (''yo'''n''' "four"), from {{nihongo2|よ}} (''yo'' "four) by analogy with Sino-Japanese {{nihongo2|三 (さん)}} (''sa'''n''' "three", originally pronounced ''sa'''m''''')

Of course, there are also some words with this sound that either lack Chinese characters or were coined in the modern or Early Modern Japanese eras, when {{nihongo2|ん}} (''n'') had been fully incorporated into the language. For example,

* {{nihongo2|さ'''ん'''}} (''sa'''n''''' "[all-purpose honorific]"), originally pronounced ''sa'''m'''''; from {{nihongo2|樣 (さま)}} (''sa'''ma''''' "[respectful honorific]") (in modern orthography, the new character form {{nihongo2|様}} is used)

Regardless of how it came to be, the Japanese orthography lacked the character {{nihongo2|ん/ン}} (''n'') or any equivalent. Therefore, until the spelling reforms of 1900, {{nihongo2|む/ム}} (''mu'') was generally used to represent the syllabic nasal. Sometimes, this convention may be preserved by modern writers, but standard historical kana distinguishes {{nihongo2|む}} (''mu'') from {{nihongo2|ん}} (''n'').

There is one exception. In classical Japanese, there is an auxiliary verb ({{nihongo2|助動詞}} ''jodōshi'') {{nihongo2|む}} (''mu'') which indicated the volitional. It, too, underwent vowel elision, and came to be pronounced as {{IPA|/m/}} and then {{IPA|/n/}}. However, the conventions of standard historical kana call for this auxiliary verb (and any word derived from it) to be written with {{nihongo2|む}} (''mu'') even though they are pronounced as {{nihongo2|ん}} (''n'').

Since the auxiliary verb {{nihongo2|む}} (''mu'') is non-existent in modern Japanese, there are no dialects that preserve the distinction expressed in this rule. However, some may preserve the distinction between final {{IPA|/m/}} and {{IPA|/n/}}.