〜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).