How does the の work in 「日本人の知らない日本語」?


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.




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 **が** 買った本
>   2. ジョン **の** 買った本
>

>
> _The book John bought_

This is true in _double-subject constructions_ as well:

>   1. ジョン **が** 背 **が** 高い理由
>   2. ジョン **が** 背 **の** 高い理由
>   3. ジョン **の** 背 **が** 高い理由
>   4. ジョン **の** 背 **の** 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 **が** 本 **を** 買った店
>   2. *ジョン **の** 本 **を** 買った店 _(ungrammatical)_
>

>
> _The store where John bought the book_




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 **が** 買った本
>   2. ジョン **の** 買った本
>

>
> _The book John bought_

This is true in _double-subject constructions_ as well:

>   1. ジョン **が** 背 **が** 高い理由
>   2. ジョン **が** 背 **の** 高い理由
>   3. ジョン **の** 背 **が** 高い理由
>   4. ジョン **の** 背 **の** 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 **が** 本 **を** 買った店
>   2. *ジョン **の** 本 **を** 買った店 _(ungrammatical)_
>

>
> _The store where John bought the book_

