~ずに
Do something without doing another action
You’ll be able to form ~ずに, including the irregular せずに, and describe an omitted action in a more formal style than ~ないで.

朝ご飯を食べずにキャンプ場を出発したので、お腹が空きました。
asagohan o tabezu ni kyanpujou o shuppatsu shita node, onaka ga sukimashita.
What do you think this sentence means?
Because we left the campsite without eating breakfast, I got hungry.
Describe an action performed without another
~ずに means "without doing..." (formal equivalent to ~ないで). It describes an action skipped or omitted while performing another.
彼は何も言わずに帰った。
kare wa nani mo iwazu ni kaetta.
He went home without saying anything.
辞書を使わずにこの本を読んだ。
jisho o tsukawazu ni kono hon o yonda.
I read this book without using a dictionary.
Replace ない with ずに
Take the verb's negative form (ない-form), drop ない, and attach ずに. Irregular: する becomes せずに (not しずに). Can also appear as plain ず at a clause break.
諦めずに最後まで練習を続けた。
akiramezu ni saigo made renshuu o tsuzuketa.
Without giving up, I continued practicing until the end.
~ないで vs ~ずに
Both mean “without doing”. ~ないで is the everyday form. ~ずに means the same but sounds a little more formal, so it is common in writing and careful speech. For する, use せずに.
~ないで, without (everyday)
傘を持たないで出かけた。
kasa o motanaide dekaketa.
I went out without taking an umbrella.
Natural in conversation.
~ずに, without (more formal)
傘を持たずに出かけた。
kasa o motazu ni dekaketa.
I went out without taking an umbrella.
Same meaning, a little more formal.
図書館の本は、カウンターで手続きをせずに持って帰ることはできません。
toshokan no hon wa, kauntaa de tetsuzuki o sezu ni motte kaeru koto wa dekimasen.
Library books cannot be taken home without going through the procedure at the counter.
男性は、拾った財布の中のお金を一円も使わずに交番に届けたそうです。
dansei wa, hirotta saifu no naka no okane o ichien mo tsukawazu ni kouban ni todoketa sou desu.
Reportedly, the man took the wallet he found to the police box without spending a single yen of the money inside.
風邪をひいたときは、無理をせずに、ゆっくり休むことが大切です。
kaze o hiita toki wa, muri o sezu ni, yukkuri yasumu koto ga taisetsu desu.
When you catch a cold, it is important to rest well without overdoing it.
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