Is "sou ka na" roughly equal to "so ka" being "is that so?" and the difference
is that "sou ka na" conveys more emotions?
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2016-06-05T05:15:35.547
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2016-06-07T09:05:49.347
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question
word-choice expressions
sou ka na and sou ka
Not in the slightest. When you say そうか 'sou ka', you are saying something like
'I see' or 'Is that so?' You have understood what the other party is saying.
When you say そうかな, you say something like 'I doubt that' or 'Really?' You are
casting doubt on the other party's claims.
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2016-06-05T05:30:29.873
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2016-06-05T05:30:29.873
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answer
Their difference is subtle, especially in everyday conversation where they
only differ in nuances rather than "real" meaning. But you can say that かな is
more "interaction-oriented" because of the な which is cognate with ね.

You can compare the dictionary definitions of
[か](http://dictionary.goo.ne.jp/jn/34861/meaning/m0u/%E3%81%8B/) and
[かな](http://dictionary.goo.ne.jp/jn/43373/meaning/m0u/%E3%81%8B%E3%81%AA/):

>   * 〔か〕質問や疑問の意を表す。  
>  〔かな〕 **念を押したり、心配したりする気持ちを込めた** 疑問の意を表す。
>
>   * 〔か〕引用した句の意味やある事実を確かめ、 **自分自身に言い聞かせる** 意を表す。  
>  〔かな〕 **自分自身に問いかけたり、自分自身の意志を確認したりする** 意を表す。
>
>   * 〔か〕（多く「…ないか」の形で） **命令** の意を表す。  
>  〔かな〕（「ないかな」の形で） **願望** の意を表す。
>
>   * 〔か〕 **反語** の意を表す。/ **難詰・反駁** (はんばく) の意を表す。  
>  〔かな〕 **理解できない、納得いかない** という意を表す。
>
>

So... if summed up, かな is more like keeping the dialog rather than one-
sided/self-contained remark, or mentioning/considering the hearer rather than
being detached/confrontational to them.

> まあ、そうか _Well, I see._  
>  まあ、そうかな _Well, I think you could say that._ (usually followed by そうだよ etc.)
>
> 本当にそうか？ _Is that so? Really?_  
>  本当にそうかな？ _Do you really think so?_

Note that "let's --" "shall we --" kind of meaning only belongs to か, and not
かな.

> 一緒に行かないか _Why don't you come with me?_  
>  一緒に行かないかな _I wonder if (they) go together._
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2016-06-07T09:05:49.347
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answer