how do I use ～んです with a noun?

Question

I'm learning to use ～んです and according to my class notes, when used with a noun it should be conjugated like " noun + な + んです".

This is just a random example but I want to make sure I'm using this properly.

Let's say someone asked: "それは　どうですか。"
Is this a correct response: "これは　ねこなんです。"

Also, if you have a more realistic example of when you would use ～んです with a noun, I'd love to see it.

Lastly, I would like to see an explanation on how to conjugate verbs with ～んです as well. I'm still a bit confused about it and my textbook is not clearing it up for me.

Thanks in advance!! :)

Answer 1

「～～な（の/ん）です/だ」 (More informal with 「ん」)

is an explanatory expression.　It is different from (and more nuanced than) a simple declarative statement describing what/how something is, which takes the form:

「～～です/だ」

If there is a cat in front of you that looks unmistakably like a cat, you will say:

「これはネコです。」

In fact, (unless you want to practice speaking Japanese,) you might not even say that because it is so obviously a cat. It could not be anything else (any other kind of animal). The point is that it would still make sense to say that.

What you will never say, however, in this situation is:

「これはネコなんです。」 ≒ "Actually, this is a cat.", "Believe it or not, this is a cat.", etc.

That will sound nonsensical, won't it?. I hear this misuse among J-learners on Japanese TV and Youtube all the time. In fact, I had been waiting for someone to ask about this here for quite some time.

So, when can we say 「これはネコなんです。」, the explanatory version?

You can say it when you have a cat that does not look like a cat -- most likely, it looks like another kind of animal.

Guy: 「それ、何{なん}の動物{どうぶつ}？キツネ？」 "What's that animal? A fox?"

You: 「これ、ネコなんです（よ）。そう見{み}えないけど。」 "It's a cat! Doesn't look like one, though."

Hope my explanation was clear enough.

With verbs, you can just add 「のです/んです」 to the dictionary form or the past tense form. No other forms will work.

Below is the image of Japan's first disposable camera named 「写{うつ}ルンです」 (see lower left corner for name). The name implies something like "It actually takes (good) pictures despite its cheap look." In other words, it is explanatory.

_{(source: naver.jp)}

Answer 2

Yes, ん is an abbreviation of の, which is not the particle の (despite what some texts may tell you), but the generic pronoun の. So what comes before it is essentially a relative clause that describes the pronoun. This is just a layer of indirection that softens the sentence and can be thought of as saying something like "The fact is that..." although it's more common in Japanese than that phrase is in English.

So you have それは　ねこだ as your relative clause, but だ cannot be used in a relative clause (this is because だ is a predicative form, so can't be used in an attributive position), so you should use the attributive particle な instead.

Another example would be something like:-

はなせば　ながい　こと　なのです

It's a long story. (Literally something like "The fact is, if I tell it, it'll be a long thing.")

For verbs it's quite simple. Verbs in the plain form are already attributive (strictly speaking the attributive and predicative forms are identical), which means they can be used in a relative clause without any alteration, so you can simply attach のです or んです after any final verb conjugated in the plain form (i.e. not the ～ます polite form or the ～おう volitional form).

Answer 3

Usually Japanese uses "これは　ねこです。". When you would like to emphasize it, you should say "これは　ねこなんです。". Perhaps it did look like a dog, but it is a cat indeed.