As touched upon in another thread, there are several nouns that exhibit a kind of vowel shift in older forms, where the ending vowel is fronted when the noun is used on its own to become /i/ or /e/, compared to unfronted vowel forms /u/ or /o/ or /a/ when the noun is used in a compound. Examples include:

  • 天: あま vs. あめ (also for 雨)
    • 天照{あまてらす}
    • 雨合羽{あまがっぱ}
  • 上: うわ vs. うえ
    • 上着{うわぎ}
  • 金: かな vs. かね
    • 金槌{かなづち}
    • 金屋{かなや}
  • 神: かむ vs. かみ
    • 神上{かむあ}がる
    • 神所{かむどころ}
  • 黄: く vs. き
    • 黄金{くがね}
  • 口: くつ vs. くち
    • 轡{くつわ} from 口{くつ} + 輪{わ}
  • 木: こ vs. き
    • 木漏{こも}れ日{び}
  • 声: こわ vs. こえ
    • 声色{こわいろ}
  • 手: た vs. て
    • 袂{たもと} from 手{た} + 本{もと}
    • 手折{たお}る
  • 月: つく vs. つき
    • 月読{つくよみ}
  • 火: ほ vs. ひ
    • 炎{ほのお} from 火{ほ}の穂{ほ}
    • 火中{ほなか}
  • 目: ま vs. め
    • 瞬{まばた}き from 目{ま} + 叩{はた}く
    • 瞼{まぶた} from 目{ま} + 蓋{ふた}

Now for the questions.

  1. Does anyone have a list of all nouns known to exhibit this kind of vowel shift?
    • Did all nouns in ancient Japanese or proto-Japanese exhibit this vowel shift?
    • If it were only some nouns, were these nouns categorizable as any clear class of nouns? As an example of a noun class, there are inseparable nouns in Polynesian languages, which generally cover things like body parts and spiritually important terms, much like many of the Japanese vowel-shift nouns that I'm aware of.
  2. Is there any clear membership in 甲類 or 乙類 for these nouns, as compared to similar nouns that don't exhibit any vowel shift? One example is 上 kami1 with the 甲類 み and that doesn't have any kamu form, vs. 神 kami2 with the 乙類 み and that does have a kamu form.
  3. What research is there into this phenomenon? Are there any specific titles or authors that cover this?
    • One theory I've read about (possibly in Shibatani's The Languages of Japan, which I've since misplaced) is that these nouns, when used in standalone contexts, were appended with the now-obsolete Old Japanese い, an emphatic nominalizing particle. Over time, this fused with the preceding vowel to produce vowel fronting. As evidence for this, the term カムイ appears in Ainu as a possible borrowing from pre-Old Japanese, before any such sound fusion, clearly manifesting a distinct む and a distinct い sound.
    • Another theory that I've only come up with on my own is that this might be somehow related to verb conjugations, where the 連用形{れんようけい} always ends in either /i/ or /e/. Verb stems, when used as nouns, always use the 連用形, at least in modern Japanese. Perhaps this is a reflection of some phonetic constraint or requirement in an ancient stage of the language, that is also reflected in these standalone noun forms?
  • 2
    See also here.
    – Zhen Lin
    Commented May 21, 2014 at 18:36
  • I've actually wondered about this too. Lots of kanji have a single 訓読み and an unfronted form followed by a tilde, such as "あめ, あま〜". I'd like to know about the unfronting like you asked, but I'd also like to know why they place a tilde after. Is it to show that it can only be used in a compound? Commented May 22, 2014 at 2:46
  • 1
    A first step could be an OJ dictionary which shows the ko-otsu distinction. Anybody got a link?
    – dainichi
    Commented May 22, 2014 at 10:52
  • 1
    @KingPumpkin, the ~ is most likely an indication that the unfronted form can only be used in compounds. Commented May 22, 2014 at 20:29
  • Frellesvig talks about this on pp.44-47 of A History of the Japanese Language (2010). Searching online, I found a very similar discussion by Frellesvig that was freely available: conf.ling.cornell.edu/whitman/… Search for apophonic.
    – user1478
    Commented Jun 11, 2014 at 12:32

2 Answers 2


Straight from jawiki on カム/神:

"カムヤマトイワレヒコ、カムアタツヒメなどの複合語で「神」が「カム」となっていることから、「神」は古くは「カム」かそれに近い音だったことが推定される。大野晋や森重敏などは、ï の古い形として *ui と *oi を推定しており、これによれば kamï は古くは *kamui となる。"

  • This matches Shibatani and others. However, this is specific to 神 kamu / kami, and does nothing to address the overall phenomenon as exhibited in many other words with different core vowels (also a and o, in addition to the u in words like 神 kamu and 口 kutu). Commented Jun 27, 2014 at 0:54
  • Addition: The article mentioned by Marcus is the 神 (神道) article on the JA Wikipedia, in the section marked 語源. The list of purported derived terms at the end of this section strikes me as most dubious, FWIW. These were all added by user ABnormal, starting from this edit. Commented Jun 27, 2014 at 1:03
  • The mentions of Turkish kam and German ham are also odd, and were added by anon users here and here. Commented Jun 27, 2014 at 1:04


The following changes may happen when forming compound words:

'e' turns into 'a' (雨宿り・金沢・船旅)
'i' turns into 'u' (くつわ・かむなぎ)
'i' turns into 'o' (木陰、木霊、最寄り)
'o' turns into 'a' (白髪・たなごころ)

If the first syllable of the second word begins with an unvoiced consonant, it often becomes voiced. 連濁です。

'ts' turns into 'tz'(横綱・手綱)
'f' turns into 'b' (まぶた)
't' turns into 'd' (酒樽)etc.

This is like the English...

"tooth" -> "teeth"
"foot" -> "feet"
"goose" -> "geese" 
"cow" -> "kye" would be an older English example)

...except that it is used in compound word formation rather than pluralization.

These words that undergo this vowel-shift are very often compound nouns of Japanese origin (複合和語名詞). Although this also happens in the 動詞 example of 「くる」⇒「こない」.

The class that these words belong to could be called 複合和語, though I don't believe that term is in general use.

  • I upvoted for your information about "our language", but you are making a huge mistake about English. Foot was once pronounced as "f - o - o -t" and it is still spelled as "foot", not "feet" ( plural ) only its sound changed to "f - u - u- t". That's why you got downvoted, I guess.
    – user7644
    Commented Feb 16, 2015 at 14:26
  • What, what, what???? English words that went the great vowel shift has nothing to to do with 造語,複合語. In English it is rather about such as capable -> capab-ility.
    – user7644
    Commented Feb 16, 2015 at 14:47
  • What I'm trying to say in the answer may not be clear. Just as you pointed out, that "vowel shift" in some Enlish plurals has nothing to do with the historical Great Vowel Shift that you mentioned. However both languages (和英) utilize vowel shifting as a linguistic device to change meaning. Japanese does it for some compound 和語, and English does it for some plural nouns. Do you know what I mean?
    – sazarando
    Commented Jun 14, 2016 at 5:08
  • I am sorry, klindly let me have time since this question was long time ago and I don't remember at all........sorry.
    – user7644
    Commented Jun 14, 2016 at 13:40

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