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JLPT N1ConstructionFormal
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だいですFormal explanation of circumstances

だいです formally closes an explanation of how or why the present action, decision, or situation came about. It often corresponds to “that is why” or “those are the circumstances,” but with a careful, accountable tone.

How the explanation is organized

First state the relevant background or reason. The final clause then names the action, decision, or outcome and closes the account with だいです. The construction does more than give a cause: it presents how matters reached the current point.

Explaining a corrective action

このたび、へいしゃかくにんそくによりせいきゅうがくあやまりがしょうじたため、しゅうせいしたせいきゅうしょさいそうしただいです

Because an error occurred in the billed amount due to insufficient verification on our part, we have resent a corrected invoice.

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The background comes first; the final clause formally explains the action taken in response.

Typical formal settings

The form is especially natural when the speaker owes the listener an explanation or is carefully stating the reason for making contact, visiting, or changing a plan.

あんぜんかくにんそうていじょうかんようしたため、かいじょうこくへんこうしただいです

Because the safety inspection took longer than expected, we changed the opening time.

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いきみなさま調ちょうへのごきょうりょくをおねがいしたく、れんらくしただいです

I am contacting you to request the local community's cooperation with the survey.

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ちょくせつけいをごせつめいするひつようがあるとかんがえ、ほんじつうかがいしただいです

Believing that it was necessary to explain the circumstances in person, I came to see you today.

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Explaining a decision

かんけいかくしょきょうしたけっらいねんぎょうけいぞくすることにしただいです

After consulting the relevant parties, we decided to continue the program next year as well.

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Three different formations

The target pattern uses a plain verb before だいです and closes a formal explanation. By contrast, a deciding noun followed by だい means that an outcome depends on that noun. A ます-stem followed by だい means “as soon as.” These are separate constructions despite sharing the same word.

にっていてんこうだいですしょうさいまりだい、ごれんらくします。

The schedule depends on the weather. We will contact you as soon as the details are decided.

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The first sentence shows the “depends on” pattern; the second shows the “as soon as” pattern. Neither is the circumstances-closing use taught on this page.

More examples

さんしゃあんぜんさいゆうせんけんとうし、かいじょうへんこうしただいです

After giving top priority to the participants' safety, we changed the venue.

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かいまねひょうげんがあったため、がいとうしょていせいしただいです

Because some wording could have caused misunderstanding, we corrected the relevant section.

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おおくのおきゃくさまからごようぼうをいただき、サービスをけいぞくすることにしただいです

Having received requests from many customers, we decided to continue the service.

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ぞんろくせいしたけっあいげんいんはんめいしただいです

After closely examining the stored records, we identified the cause of the malfunction.

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みなさまにこれまでのけいをおつたえしたく、このせつめいかいもうけただいです

We arranged this briefing because we wished to explain the events leading up to this point.

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どうようもんだいふせひつようがあるとはんだんし、かくにんじゅんかいていしただいです

Having determined that it was necessary to prevent similar problems, we revised the verification procedure.

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