There are a number of Japanese words which have distinct compounding forms:

  • -a/-e alternation: 天・雨、酒、上、風、目 — many examples.
  • -u/-i alternation: 神([神]{かむ}[集]{つど}ふ)、月([月]{つく}[読]{よみ})
  • -o/-i alternation: 木([木]{こ}の[葉]{は})、火(炎【ほのほ】)
  • -a/-o alternation: 白([白]{しら}[雪]{ゆき})

This BBS post has more examples. There is also another kind of alternation I know of, even rarer:

  • s-insertion: 雨([春]{はる}[雨]{さめ})、青([真]{ま}っ[青]{さを})

I have three questions:

  1. Are there any other alternations I have missed?
  2. Is there an exhaustive listing of words with exceptional compound forms somewhere?
  3. To what extent is this process still alive? For instance, [風]{かざ}[車]{ぐるま} is a comparatively recent coinage.
  • I had never thought that 春雨 and 真っ青 have anything in common. Commented Aug 8, 2011 at 13:57
  • @Tsuyoshi: It is a bit of a stretch, yes. It may well be that 雨 is unique with this property. (By my count, the デジタル大辞泉 at goo.ne.jp has 11 examples of 〜さめ compounds.)
    – Zhen Lin
    Commented Aug 8, 2011 at 14:04
  • I think 真っ青 is read with an お not を. Interesting question btw.
    – Lukman
    Commented Aug 8, 2011 at 14:19
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    船/舟 ー ふね or ふな.
    – istrasci
    Commented Aug 8, 2011 at 14:23
  • @Lukman: I am using historical orthography for consistency. (For example, it seems 神集ふ is extinct in modern Japanese.)
    – Zhen Lin
    Commented Aug 8, 2011 at 14:28

2 Answers 2


As I commented earlier, I am pretty sure that much of these alternations are due to phonological rules. I realized that, among your patterns, a/e-alternation and u/i-alternation follow naturally from assuming:

  1. 露出形 vs. 被覆形 alternation hypothesis (which you also mention) as in my answer in Why is a place that sells さけ a さかや?
  2. The phonological rule described in my answer in What does こまけー mean?
  3. The long vowel mentioned in 2. above was shortened.

However, this does not explain your o/i-alternation and a/o-alternation. This fact suggest two possibilities: (1) the underlying verb is of somewhat different quality, and assuming an appropriate underlying vowel, these alternation actually fit the rule mentioned in 2, or (2) there is another rule in addition to the one mentioned in (2).

To the extent that this theory is correct, it predicts that there can be o/e-alternation such that in compound forms, ends with [o], and in isolated forms, ends with [e].


1) I don't think that you have missed anything or that you should really be concerned about it too much. Even without exhaustive research, people who know a lot about kanji know that these readings stand out as being special. Perhaps one of the readings is used in two, rather than just one word, but the sound would still seem unique in comparison to the variety of words used with the other readings. So, I hope my 90%-sure "yes" can set your mind at ease?

2) This link goes directly to a page with a list of kanji with readings that appear exclusively in one word.

3) Are words like this still being created? Yes. To what extent? That's a more difficult question. People are still doing it quite often for names, and I imagine it happens with some frequency as new words are created to describe things (e.g., in science). It's hard to quantify, especially because I wasn't able to uncover a list of 'new words' in Japanese. 日本語の新しい言葉/日本語のつぐに作った言葉とか.... These google keywords don't turn much up, but I'll try to be more creative for your cause and do a little more searching.... Anyway, I hope it's sufficient to say 'it's not a dead practice'.

It seems to me, the reason people use these "distinct" readings is because they're easier to say. I think some strange English sentences are thought of in the same way. You can tell by saying tongue twisters. They force your cheeks to go in-and-out, or your tongue to thrash to-and-fro in such a meticulous manner. For strange English sentences, saying them normally has the same effect. In Japanese, try saying "MOkuNOha", then "KInoHA", and then try saying "konoHA". The upper-case indicate open cheeks, and the lower-case indicate closed cheeks. It's easier to move your cheeks from in to out, rather than out, to in, to out, to in, so I think we just elect this simple variation.

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    I do not think that the original form of このは (木の葉) is もくのは. Commented Aug 11, 2011 at 18:17
  • I was just going through the possibilities to show how much more difficult alternative spellings could be to enunciate. Try saying this, and notice how your cheeks move in and out: "A big bug bit a bold bald bear and the bold bald bear bled blood badly; brisk brave brigadiers brandished broad bright blades; the sixth sick sheik's sixth sheep's sick." Commented Aug 13, 2011 at 9:32
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    Your reply does not seem to be relevant to my comment. Your answer suggests that きのは was derived from もくのは because the former was easier to pronounce. That is false. Commented Aug 13, 2011 at 12:56
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    Pronunciation is not the only reason why some form is used and other forms are not. I do not think that このは was chosen over もくのは because of pronunciation, and I think that your comparison between このは and もくのは is irrelevant. Commented Aug 14, 2011 at 11:42
  • 2
    From your own comments: “I suggested that konoha was used rather than kinoha or mokunoha because it's easier to pronounce.” “I don't think that konoha was chosen over mokunoha because of pronunciation, […]” You seem to have a difficulty keeping your opinion consistent. Commented Aug 14, 2011 at 12:30

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