一旦
Once …, If … for a short time, Temporarily (stop), For now or the time being
Structure
一旦 + Verb［たら］
一旦 + Verb + と
Explanation
The adverb 一旦, which can mean 'for a moment' or 'temporarily', is used to express the idea that 'once (A) happens, then (B) follows'. This meaning is most prominent when it is used with conditional forms like ば, と, or たら. In these cases, the second part of the sentence (B) often contains a negative verb, implying that reversing the initial action or state will not be easy for some time.
Common English equivalents also include 'for the time being' and 'for now'.
You will most often find 一旦 placed at the very beginning of a sentence, or immediately preceding a verb that is conjugated into the ば, と, or たら form.
- 一旦慣れれば、そんなに難しくないですよ。Once you get the hang of it, it's not that difficult.
- このおもちゃは一旦壊れたら、もう直せません。Once this toy is broken, it can't be fixed.
- このドアは一旦外に出ると、中からは開けられない。Once you go out this door, you can't open it from the inside.
Fun-fact
一旦 stems from a noun with the same characters, meaning 'one morning' or 'a brief moment'. The kanji 旦 itself represents 'dawn' or 'daybreak'. Thinking of it this way can be a helpful mnemonic; 一旦 marks the 'dawn' of a new situation that will continue for a period before it can change again.
Examples
一旦ブラックコーヒーの味を覚えたら、もう砂糖は入れられなくなる。
Once you get used to the taste of black coffee, you won't be able to put sugar in it anymore.
一旦スマホに慣れてしまうと、それなしの生活は考えられない。
Once you get used to a smartphone, you can't imagine life without one.
一旦信頼を失うと、取り戻すのは難しい。
Once trust is lost, it is difficult to get it back.
一旦この仕事を引き受けたら、最後まで責任を持つべきだ。
Once you take on this job, you should see it through responsibly to the end.
一旦ソファで寝てしまうと、ベッドまで移動するのがおっくうになる。
Once you fall asleep on the sofa, it becomes a hassle to move to the bed.
一旦契約にサインすれば、簡単には解約できません。
Once you sign the contract, you cannot easily cancel it.
一旦真実を知ってしまえば、彼のことを前と同じようには見られない。
Once you know the truth, you won't be able to see him in the same way as before.
一旦自転車の乗り方を覚えれば、決して忘れることはない。
Once you learn how to ride a bicycle, you never forget.
一旦焼きたてのパンを食べると、もう店で買う気にはなれないよ。
Once you eat freshly baked bread, you won't feel like buying it from the store anymore.
一旦彼が何かを決めると、絶対に意見を変えない。
Once he decides on something, he never changes his mind.
一旦このゲームをやり始めると、時間を忘れてしまう。
Once you start playing this game, you completely lose track of time.
一旦海外へ旅に出れば、世界に対する見方が変わるだろう。
Once you travel abroad, your perspective on the world will likely change.