いったん～ば／と／たら (ittan): Once; for a time
～いったん～ば／と／たら (ittan)
Meaning
Once; for a time
Formation and usage
いったん + conditional／clause
Notation: N = noun; V dictionary = dictionary-form verb; V stem = the stem before ます; plain clause = plain-form clause; negative stem = the form before ない. Follow the attachment shown above.
Explanation
With a conditional, describes a state difficult to reverse once reached; it can also mean temporarily.
Examples
いったん会議が始まると、途中では入れません。
Once the meeting starts, you cannot enter partway through.
いったん試験が始まると、途中では入れません。
Once the exam starts, you cannot enter partway through.
いったん研修が始まると、途中では入れません。
Once the training session starts, you cannot enter partway through.
いったん発表会が始まると、途中では入れません。
Once the presentation event starts, you cannot enter partway through.
いったん面接が始まると、途中では入れません。
Once the interview starts, you cannot enter partway through.
How related patterns differ
かけ leaves an action unfinished; たきり leaves a subsequent action absent. も同然だ treats a state as practically reached; ところだった nearly reaches it but avoids it. ばそれまでだ makes a consequence final; いったん can mean once or temporarily.