website/content/wiki/japanese/zu-nu.md

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〜ず and 〜ぬ

The suffixes 〜ず and 〜ぬ are both classical versions of the suffix 〜ない. In fact, they are two conjugations of the same word, 〜ぬ being the [連体形]{れんたいけい} form of 〜ず in Classical Japanese. However, there is also another 連体形 form of 〜ず which happens to be 〜ざる.

〜ない, 〜ざる and 〜ぬ can all be used interchangeably:

• 知らない人
• 知らざる人
• 知らぬ人

According to this post the 〜ざる form was more commonly used in [漢文]{かんぶん} while the 〜ぬ form was more commonly used in [和文]{わぶん}.