JLPT Grammar – 4 types of “〜のだ”

Table of Contents

1. 4 types of “〜のだ”
2. How to Use “〜のだ” and Its Rules
3. Explanation
4. Rephrasing
5. Assertion
6. Understanding / Realization
7. Summary
8. Similer Articles
9. Comment

Q: When is “〜のだ” used?

A: “〜のだ” has four main uses: explanation, rephrasing, assertion, and realization. This article explains each of them in detail with example sentences.

〜のだ

[Rule]
[V] Verb plain form + のだ
[A] い adjective plain form + のだ
[Na] な adjective + のだ / な adjective plain form + のだ　　*“だ + のだ” is not possible
[N] Noun + な + のだ / Noun plain form + のだ　　*“だ + のだ” is not possible
*“のだ” is often used in written language, while in spoken language it appears as “んだ” or simply “の” (the latter is common in women’s or children’s speech).

[Examples]
今日きょうは早はやく帰かえりますね。用事ようじがあるんです。（Explanation）
I will go home early today. I have something to do.

彼かれはどんなときも諦あきらめない。努力どりょく家かなんだ。（Rephrasing）
He never gives up. He is a hard worker.

何なにがあってもこのプロジェクトは成功せいこうさせるのだと心こころに誓ちかいました。（Assertion）
No matter what happens, I swore in my heart that I will make this project succeed.

A：田中たなかさんはカナダに留学りゅうがくする予定よていらしいよ。
B：だから英えい会話かいわに通かよっているんだ。（Understanding / Realization）
A: I heard Tanaka will study abroad in Canada.
B: That’s why he goes to English conversation school.

[Explanation]

It is used when the speaker wants to explain a reason or situation to the listener.
It plays the role of clearly conveying the circumstances or the speaker’s feelings.

[Examples]
財布さいふを失なくして困こまっているんです。
I lost my wallet, so I’m in trouble.

あのとき泣ないたのは、ただ悔くやしかったのだ。
The reason I cried at that time was only because I was frustrated.

A：いつもそのネックレスをつけてるね。
B：ハワイで買かって、とても気きに入いっているの。
A: You always wear that necklace.
B: I bought it in Hawaii, and I like it very much.

When only one part is being negated, “のではない” or “んじゃない” is used.

[Examples]
英語えいごはオーストラリアで勉強べんきょうしたんじゃないです。カナダで勉強べんきょうしたんです。
I didn’t study English in Australia. I studied it in Canada.

わたしが考かんがえたのではなく、山田やまださんが考かんがえたのです。　
It was not me who thought of it. It was Mr. Yamada.

書類しょるいの準備じゅんびは山田やまださんがしたんじゃなくて、木村きむらさんがしたんです。
It was not Mr. Yamada who prepared the documents. It was Mr. Kimura.

When used with an interrogative word
When combined with an interrogative word, it becomes an expression for asking the listener for a reason or explanation.

[Examples]
A：どうして遅おくれたんですか。　
B：すみません、電車でんしゃが遅おくれていたんです。
A: Why were you late?
B: Sorry, the train was delayed.

A：どうしたの？
B：この漢字かんじの読よみ方かたが分わからないんだ。
A: What’s wrong?
B: I don’t know how to read this kanji.

A：何なにで東京とうきょうに行いくんですか。
B：バスと新しん幹線かんせんで行いくつもりです。
A: How will you go to Tokyo?
B: I plan to go by bus and Shinkansen.

[Rephrasing]

It is used when summarizing what has been mentioned earlier in different words or rephrasing it to make it easier to understand. It is often followed by words such as “in other words,” “that is to say,” or “to put it differently.”

[Examples]
彼女かのじょは気分きぶん次第しだいで来きたり来こなかったり…要ようするにただ自分じぶん勝手かってなんだ。
She sometimes comes and sometimes doesn’t, depending on her mood. In short, she is just selfish.

彼かれはよく勉強べんきょうする。つまり、努力どりょく家かなのだ。
He studies a lot. In other words, he is a hard worker.

この野菜やさいは虫むしがついているけど、言いい換かえれば農薬のうやくをあまり使用しようしていないのです。
This vegetable has insects on it. In other words, it has not used much pesticide.

彼かれは人前ひとまえで話はなすのが苦手にがてです。要ようするにシャイなんです。
He is not good at speaking in front of people. In short, he is shy.

[Assertion]

It is also used when the speaker wants to strongly state their own opinion or determination. Especially when combined with words like “absolutely” or “surely,” it expresses firm intention or strong feelings. In conversation, it is often used in situations where emotions are heightened.

[Examples]
絶対ぜったいに次つぎの試験しけんには受うかりたいんだ！
I really want to pass the next exam!

健康けんこうのために、今日きょうから毎日まいにち走はしるのです。
For my health, I will start running every day from today.

母親ははおや：もう5時じだから帰かえろう。
子供こども：嫌いやだ、まだ遊あそぶの！！
Mother: It’s already five o’clock, so let’s go home.
Child: No, I don’t want to! I still want to play!!

[Understanding / Realization]

It is used in response to the preceding sentence or the listener’s statement, often together with “that’s why” or “so,” to express that the speaker has come to an understanding of the fact or situation. Compared to using just “〜だ,” it emphasizes the nuance of the conclusion making sense or being convincing.

[Examples]
A：木村きむらさん、海外かいがいに転勤てんきんになったそうですよ。
B：ああ、だから最近さいきん見みかけないんだ。
A: I heard Mr. Kimura was transferred overseas.
B: Oh, that’s why I haven’t seen him recently.

あの子こは毎日まいにちピアノを練習れんしゅうしているのか。それであんなに上手じょうずなんだ。
So that child practices the piano every day. That’s why he is so good.

先生せんせいは体調たいちょうを崩くずしていたんですね。それで授業じゅぎょうが休やすみだったんだ。
I see, the teacher was not feeling well. That’s why the class was canceled.

Summary

Usage	Rule	How to use	Examples
①Explanation	[V] Verb plain form + のだ [A] い adjective plain form + のだ [Na] な adjective + のだ / な adjective plain form + のだ [N] Noun + な + のだ / Noun plain form + のだ	Used when the speaker wants to explain a reason or situation. When only one part is being denied, “のではない / んじゃない” is used. By making a question form, it is also used to ask the listener for an explanation or reason.	財布さいふを失なくして困こまっているんです。 I lost my wallet, so I’m in trouble. わたしが考かんがえたのではなく、山田やまださんが考かんがえたのです。 It was not me who thought of it. It was Mr. Yamada. A：どうしたの？ B：この漢字かんじの読よみ方かたが分わからないんだ。 A: What’s wrong? B: I don’t know how to read this kanji.
②Rephrasing		Used when restating or summarizing what was mentioned earlier. Often followed by words like “つまり” (in other words) or “要ようするに” (that is to say).	彼かれはよく勉強べんきょうする。つまり、努力どりょく家かなのだ。 He studies a lot. In other words, he is a hard worker.
③Assertion		Used when the speaker strongly states their opinion or determination. When used together with words like “絶対ぜったいに” (absolutely) or “必かならず” (surely), it conveys an even stronger will.	絶対ぜったいに次つぎの試験しけんには受うかりたいんだ！ I really want to pass the next exam!
④Understanding / Realization		Based on a preceding statement or fact, the speaker expresses realization or agreement, often accompanied by “だから / それで” (“that’s why / so”). Compared to just “～だ,” using “～のだ” emphasizes the nuance of realization.	A：木村きむらさん、海外かいがいに転勤てんきんになったそうですよ。 B：だから、最近さいきん見みかけないんだ。 A: I heard Mr. Kimura was transferred overseas. B: Oh, that’s why I haven’t seen him recently.

Similer Articles

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