If you convert "ななにち" or "しちにち", you can get a letter "㏦(IDEOGRAPHIC TELEGRAPH SYMBOL FOR DAY SEVEN). Doing "きゅうにち" or "くにち", you can get a letter "㏨(IDEOGRAPHIC TELEGRAPH SYMBOL FOR DAY NINE). When I say the 7th or 9th day of the month, instead of "なのか" or "ここのか", "にち" form is often used. Question is here:

i) You can also use "にち" form rather than "なのか" for the 7th. In this case, are both "ななにち" and "しちにち" used?

ii) You can also use "にち" form rather than "ここのか" for the 9th. In this case, are both "きゅうにち" and "くにち" used?

One more: When we count 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, they will be "じゅう、にじゅう、さんじゅう、よんじゅう、ごじゅう、ろくじゅう、ななじゅう、はちじゅう、きゅうじゅう、ひゃく". Why are the expressions "じゅう for 40, しちじゅう for 70 and じゅう for 90" wrong?

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    I (again!) note that, while it's fine to specify that you'd like a native speaker's opinion, you could be more polite in doing so. Your question is reaching the fairly diverse Japanese Language Stack Exchange community, and it's not clear why a non-native speaker couldn't answer this question well, so it seems quite dismissive to me to simply start your question with "I'm asking a native Japanese speaker". I appreciate your mother tongue may not be English, so this is not intended as a personal criticism; rather, it is meant as advice to bear in mind, to enable you to make the most of JL SE.
    – henreetee
    May 30, 2020 at 23:40
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    @henreetee yeah, it lends the impression that non-native speakers can't properly answer questions about basic topics in Japanese.
    – Leebo
    May 30, 2020 at 23:56
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    And native speakers are sometimes terribly bad at explaining simple things. As a native Japanese member of this site, I "studied" how to explain the difference between は and が (it was much more complicated than I thought), but I still cannot explain the difference between たら and れば logically :)
    – naruto
    May 31, 2020 at 0:11

1 Answer 1


Always say なのか and ここのか, and don't use ななにち/しちにち/くにち/きゅうにち. They are understandable, but wrong. They are as wrong as saying "fiveth" instead of "fifth". But we do say じゅうななにち/じゅうしちにち (17th), にじゅうきゅうにち/にじゅうくにち (29th), etc.

The IME I usually use (ATOK) does not recognize ななにち and くにち as a word, and of course it does not convert them to ㏦ or ㏨. It looks like MS-IME somehow "knows" ななにち and くにち, but I would say it's an idiosyncratic behavior. Sometimes IMEs intentionally include a wrong reading of a word for the sake of convenience, so you should not use them like authoritative dictionaries. For example, ATOK "knows" ふいんき, which is a wrong reading of 雰囲気 (ふんいき; "atmosphere"). MS-IME does not know such a reading.

On the other hand, しじゅう, しちじゅう are not wrong, but it sounds old or dialectal. くじゅう is now rare except in certain proper nouns. よん and なな are more distinctive than いち/しち/し, so they are preferred, especially in math and financial contexts.

  • I asked @Mitsutoshi Watanabe in "japanese.stackexchange.com/questions/77696/the-day-of-the-month", "にち" form is often used even if "か" form is available. The answered person is also a native speaker. So, in my sense, "にち" form is not wrong and often used, but "か" form is more used. You can say both "つ" form and "こ" form for 7 or 9 things. What I want to ask is: "ななにち" vs "しちにち" and "きゅうにち" vs "くにち".
    – Niconii
    May 30, 2020 at 23:47
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    @Niconii I'm also a native speaker :) いちにち is perfectly fine when you refer to a length of time, but people around me never say ににち/さんにち and so forth, and you must not think it's an often-used expression. We safely say じゅうはちにちめ, so there may be a few people who says はちにちめ is also fine when explicitly asked, but I believe even such people use only ようかめ when they speak naturally.
    – naruto
    May 31, 2020 at 0:03

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