I've read that 日本人の知らない日本語 translates to: "Japanese (language) that Japanese (people) don't know". But I don't understand how or what the の does in that sentence. If I'm not mistaken 知らない日本語 could mean "Japanese language that (x) don't know" or "even unknown Japanese". But I don't get how the 日本人の fits into the translation.

2 Answers 2


In your example, 日本人の知らない is a relative clause, equivalent in meaning to 日本人が知らない. This clause as a whole modifies 日本語, so it means the Japanese that Japanese people don't know.

In relative clauses, the subject particle が can be replaced with の:

  1. ジョン買った本
  2. ジョン買った本

The book John bought

This is true in double-subject constructions as well:

  1. ジョン高い理由
  2. ジョン高い理由
  3. ジョン高い理由
  4. ジョン高い理由

The reason John is tall

But you can't replace が with の if there's a direct object marked with を:

  1. ジョン買った店
  2. *ジョン買った店 (ungrammatical)

The store where John bought the book

  • 7
    Maybe I am beating the dead horse, but ジョンの本を買った店 can mean "The store someone bought the book written by John."
    – eltonjohn
    Commented Jun 26, 2015 at 13:06
  • 9
    When I say "ungrammatical", to be more precise I really mean "ungrammatical with the intended interpretation". That is, the process of nominative-genitive conversion is ungrammatical here due to the transitivity restriction, even though there may be an alternative source for the example in question, as you point out. Thank you for your comment!
    – user1478
    Commented Jun 26, 2015 at 20:52
  • 2
    In the last two sentences using を, they both strike me as grammatical, but the meaning shifts -- sentence 2 parses out to "the store that bought John's book". Commented Nov 13, 2015 at 7:14
  • 1
    Please see my comment above :-)
    – user1478
    Commented Nov 13, 2015 at 10:39
  • Interestingly enough, can be used in 文語 Japanese where in modern, oral Japanese only is usually acceptable (我々が心), as is obvious in a bunch of place names (written -- e.g. 関ケ原, 霞ヶ関 etc). Maybe and where more broadly interchangeable in different times / regions, but only clearly remained so in the case of relative clauses in modern / standard Japanese ?
    – desseim
    Commented Aug 31, 2019 at 17:34

It's just standard GA-NO conversion.

'Japanese that [Japanese don't know]'

  • 9
    In more precise terms: の can act like a subject (nominative) particle in descriptive (attirbutive/relative) clauses.
    – ithisa
    Commented Sep 14, 2013 at 23:26

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