What it means
なしに expresses the absence of something necessary or the failure to perform an expected action, meaning “without” or “without doing.” It is formal and is especially common in written, official, academic, and serious contexts. It attaches directly to a noun, or to a verb in the pattern verb dictionary form + ことなしに. The construction often implies that the following action or result occurred despite the missing condition, or that it cannot properly occur without it. The sentence-ending form can still be changed independently to show familiar or polite register.
Usage note
なしに is considerably more formal than なしで and should not be used merely to make an ordinary casual sentence sound natural. With verbs, the nominalizing こと is normally required; a direct combination such as 行くなしに is not standard. Do not confuse it with なしでは, which means “if there is no...” or “without..., it is not...,” and commonly introduces a restriction or negative judgment.
How to use it
事前の許可なしに、施設へ入ることはできません。
It is not possible to enter the facility without prior permission.
彼は十分に検討することなしに、計画を変更しました。
He changed the plan without sufficiently considering it.
事前の許可なしに、施設へ入ることはできない。
It is not possible to enter the facility without prior permission.
彼は十分に検討することなしに、計画を変更した。
He changed the plan without sufficiently considering it.
Example sentences
本人の同意なしに、個人情報を第三者へ提供してはならない。
Personal information must not be provided to a third party without the person's consent.
十分な検討なしに、研究計画を変更することはできない。
The research plan cannot be changed without sufficient consideration.
専門家の助言なしに、この装置を修理することは危険である。
Repairing this device without expert advice is dangerous.