Explanatory 「の」 usage

So, I was reviewing the explanatory 「の」 Tae Kim’s grammar guide, and I got a bit confused when it started talking about attaching the「んだ」to various words vs conjugating the「んだ」itself.

For example, what would be the difference between the following?
「学生じゃないんだ」vs. 「学生なんじゃない」
「学生だったんだ」vs. 「学生なんだった」
「学生じゃなかったんだ」vs. 「学生なんじゃなかった」

I’m also a little confused about using both at the same time. The guide gives this example: 「 その人が買うんじゃなかったの」and I have no idea how the addition of the 「の」in both places changes the meaning of the sentence (from, say, saying「その人が買うんじゃなかった」and「その人が買わなかったの」).

If anyone could help shed some light on this, I’d be super grateful. Thank you!

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The location usually denotes the explanatory part:

「学生じゃないんだ」vs. 「学生なんじゃない」

“I’m not a student.” (General explanation, no real emphasis)
“I’m not a student.” (Emphasis on the student part, like, I’m not a student I’m a teacher)

In this case, the explanatory part is emphasizing both things.


Also I believe「学生なんじゃない」is often, though not always, used as a question seeking explanation like ‘Aren’t you/he/she/they a student?’


Do you mean to say 「その人が買うんじゃなかったの」is emphasizing both the not buying and why the buying didn’t happen?

Yes, but note that depending on the tone or common usage it can be a question as well as @ObolioJ noted.


Thank you!

Cure Dolly had a video about this and her approach was very memorable to me.
The の at the end of the sentence is the same one used to nominalize verbs. It nominalizes the whole sentence in this case. 〇のだ would translate to something like “It is that 〇”

「学生じゃないんだ」It’s that I’m not a student.
「学生なんじゃない」It not that I’m a student.

Do you happen to have a link? Don’t think I’ve watched Cure Dolly before…

Warning: A lot of people find Cure Dolly pretty annoying, though I like her way of explaining Japanese.


That was strangely disconcerting.

Thank you! I don’t think I’ve heard anyone explain sentences in similar ways, and this was an interesting way to think about the 「の」 usage, so I’ll be checking out her other videos to see if they help clarify other grammar points for me.

It’s actually pretty similar to the wording Tae Kim uses in your link:

  • 今は忙しい
    Is it that (you) are busy now? (gender-neutral)

Alice: Where is it that (you) are going?

アリス:その人が買う んじゃなかったの
Alice: Wasn’t it that that person was the one to buy?

ボブ:ううん、先生が買う んだ
Bob: No, it is that teacher is the one to buy.

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You’re right! I think I focused too much on the smooth translations Tae Kim provided and that probably added to my original confusion.

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Ah, not annoying, just extremely uncanny valley.

Plus the lingering suspicion that the voice is a man’s with modulation software.


Oh good, I’m not imagining things.

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Which, to be fair, isn’t too uncommon in the anime scene. lol

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And… just blatantly wrong pronunciations. I accidentally clicked on one the other day and immediately cringed at the “Ko-nitchy-wa”

I don’t understand why they find that acceptable.

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