〜ずに
Without doing… (written, formal)machine translation
FormationVerb ない-form (drop ない) + ずに (exception: する → せずに)
〜ずに means "do B without doing A," equivalent to the 〜ないで you know well from N4 but with a more written, formal flavor: 朝ご飯を食べずに出かけた (went out without eating breakfast). In everyday speech Japanese speakers still prefer ないで; ずに appears frequently in writing, newspaper articles, and exams.
Formation: take the ない-form, drop ない, and add ずに: 食べない → 食べずに, 言わない → 言わずに. The one exception to remember is する → せずに (not しずに): 勉強せずに (without studying…).
Note that ずに can replace ないで only in the sense "in a state of not doing A"; it cannot replace the prohibition 〜ないでください or the causal sense of 〜なくて. In even stiffer writing you may encounter ず standing alone mid-sentence: 何も言わず、部屋を出た.
Examples
朝ご飯を食べずに学校へ行きました。
I went to school without eating breakfast.
辞書を使わずに、この記事が読めますか。
Can you read this article without using a dictionary?
彼は何も言わずに部屋を出て行った。
He left the room without saying a word.