57720
As I understand it, the copula "だ" turns into "な" in some situations. The most
obvious one is after な-adjectives, but it often appears after nouns too, like
in this sentence: "スミスさんは、将来日本の会社で働くのが夢なんだって".

Are there any rules for when だ turns into な? It seems to me that if the copula
shows up at the end of a sentence it's "だ" and elsewhere it's "な", but I have
no idea if it's that simple.
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2018-04-04T03:36:40.027
57715
2018-04-04T15:27:16.197
2018-04-04T04:26:05.820
27104
27104
question
usage copula
When do you use the "な" version of the copula?
> when does the copula become "な"?

Simply, だ turns into な when it modifies the following noun, which is の/ん in
this case. な is the attributive form of the copula だ. So-called _na_
-adjectives and ordinary nouns are [technically both
nouns](https://japanese.stackexchange.com/a/1016/5010), so they share the
similar grammar pattern.

This の/ん is a tiny special _noun_ commonly referred to as _explanatory-no_.
This の/ん is a big topic in Japanese, so please read these first:

  * [What is the meaning of ～んです/～のだ/etc?](https://japanese.stackexchange.com/q/5398/5010)
  * [Wasabi - Explanatory のだ （んだ）](https://www.wasabi-jpn.com/japanese-grammar/explanatory-noda/)

So, 夢なのだ/夢なんだ has an added nuance as compared to simple 夢だ.
"スミスさんは将来日本の会社で働くのが夢なんだって" may be used in the following situations:

  1. When this sentence works as an explanation/clarification of the previous context. 

> スミスさんは毎日、日本語を一生懸命勉強してるよ。将来日本の会社で働くのが夢な **ん** だって。

  2. When this sentence works as a preliminary remark (i.e., background information). 

> スミスさんは将来日本の会社で働くのが夢な **ん** だって。お勧めの会社を知ってたら紹介してくれない？

  3. When you just realized this fact. 

> ねえ、今本人から聞いたんだけど、スミスさんは将来日本の会社で働くのが夢な **ん** だって!
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2018-04-04T15:27:16.197
57720
2018-04-04T15:27:16.197
5010
57715
answer