一旦

いったん

once, for a moment

JLPT N2

Character Breakdown

Usage of 一旦

The word 一旦 is used to indicate that once a certain condition or event happens, something else will follow. It often translates as "once" or "in case" in English. It implies a cause-effect relationship and is commonly used to warn, advise, or describe consequences.

Common contexts

  • Expressing a condition that triggers a result: 一旦 + [event], [result].
  • Often used in formal or semi-formal speech, especially in instructions or warnings.

Collocations and patterns

  • 一旦决定 (once decided): emphasizes finality and encourages commitment.
  • 一旦发生 (once it happens): used for emergencies or unexpected events.
  • 一旦习惯 (once accustomed): indicates a change in state after adaptation.

Nuances

Using 一旦 suggests that the event is likely or important enough to cause a significant change. It differs from simpler conditionals like 如果 (if) by stressing immediacy or inevitability once the event occurs.

Common confusion

Don't confuse 一旦 with 一直 (yīzhí), which means "continuously". 一旦 focuses on a single point of change or occurrence, not duration.

Example Sentences

Once you have decided, don't regret it.

In case of an emergency, please call the police immediately.

Once you get used to this method, your work will be more efficient.

Once you miss this opportunity, it will be hard to get another.

Once the weather turns cold, everyone starts wearing thick clothes.