ず (zu): Without doing
～ず (zu)
Meaning
Without doing; not doing
Formation and usage
Remove ない from the negative verb form and add ず. Irregular forms: する → せず; 来る → 来ず (こず). Use ずに before another action.
Explanation
A negative form often used in writing or formal speech. Zu ni means performing an action without doing another one first; zu can also connect a negative clause to what follows. Suru becomes sezu, not shizu.
Examples
辞書を使わずに、この文章を読みました。
I read this passage without using a dictionary.
彼は何も言わずに席を立ちました。
He got up from his seat without saying anything.
予約をせずに店へ行ってしまいました。
I went to the restaurant without making a reservation.
休まずに働くと、体を壊します。
Working without a break will damage your health.
理由が分からず、先生に質問しました。
I did not understand the reason, so I asked the teacher.
How related patterns differ
なかなか～ない describes a desired result that does not come easily. ず negates an action or means without doing, without itself implying a long wait. だらけ describes a state full of usually undesirable things, not a negative verb form.