〜ず

About

〜ず can be attached to the negative stem form of a verb, with する and 来くる being exceptions: 「せず・来こず」.

〜ず may be used in place of 〜なくて to form "didn't do X, so Y" type statements. (〜ず is more common than 〜なくて in written/formal situations.)

E.g. 昨日きのうはよく寝ねれず、今日きょうはすごく疲つかれている。 "I didn't sleep well yesterday, so I'm very tired today."

〜ず・〜なくて can also occasionally be used to list two (or more) negative aspects of something, without a cause-and-effect relationship.

E.g. 窓まども開あかず、ドアも開あきません。 "The window won't open, and neither will the door."

Summary

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  The ず form of a verb may be used in place of 〜なくて to form "didn't do X, so Y" type statements

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  〜ず is more common than 〜なくて in written/formal situations

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  〜ず・〜なくて can also occasionally be used to list two (or more) negative aspects of something, without a cause-and-effect relationship