Is there a difference (or nuance) or is it just two ways of saying the same
thing?

For example, どうして、とぶか？ （１） こわいんです。 （２） こわいですから。

Obviously, those are very simple examples. But are there times where you
couldn't use one in place of the other to explain "why" you did something (or
you did something "because")?
CC BY-SA 3.0
2012-12-11T23:03:40.873
9751
2012-12-13T04:17:51.380
769
question
word-choice
Difference between kara and n desu?
「んです」,「んだ」and friends give a nuance of conveying new information or explaining
something to someone for the first time.

「からです」etc. is just a reply to some explicit question of why.

For example, something like this conversation might have both with very
different meanings/nuances:

> さち：dotnetN00b、もう退社してる？[dotnetN00b, you're already leaving work?]
>
> dotnetN00b: ううん。サーティワン行くんだよ。ついてくる？ [No, I'm going to Baskin Robin's! Wanna
> come?]
>
> さち：いきなりどうして？ [Whoah, that's out of the blue. Why you going?]
>
> dotnetN00b: サーティワン、マージうまいからだよ！毎日食っちゃってる。ふふん。 ['cause Baskin Robin's is
> ridiculously good! I go there every day. :P]

Clear as mud?
CC BY-SA 3.0
2012-12-12T01:22:54.877
9752
2012-12-12T01:27:35.840
2012-12-12T01:27:35.840
921
1565
9751
answer
I am giving a guess here, so feel free to take shots at this. I am assuming
that the ん is の acting as a nominalizer. I will translate from literal to
natural.

（１） こわいんです。 → こわいのです。

Scariness exists. → (Because) scariness exists. → "'Cuz it's scary." (The "it"
here is assumed by me)

の here is a nominalizer, which perhaps we can think of as turning the
adjective こわい into a noun= scariness.

（２） こわいですから。

Scary is because. → "Because I am scared." (assuming the subject is "I")

Technically, こわいですから may not be correct, though one does hear it colloquially.
It might make more sense to say:

こわいから。or こわいからです。

see:

[What is 〜からです and when is it used? How does it differ from 〜ですから and
〜んです?](https://japanese.stackexchange.com/questions/6903/what-
is-%E3%81%8B%E3%82%89%E3%81%A7%E3%81%99-and-when-is-it-used)

Take further note that こわい is a tricky word to use here, because it can both
describe the state of being frightened or something frightening. (*I am not
sure of the validity of this claim :p)

Also, because of the lack of information I, as a reader, have on this
conversation, I cannot accurately ascertain the subject or object being
described (as would be necessary to accurately translate into English.)

I also think that どうして、とぶか is somewhat unnatural, especially if you wanted to
say "Why'd you jump?" However, I am a novice at the Japanese language, so take
my opinion with a grain of salt, especially if you found this conversation
from a reliable source.
CC BY-SA 3.0
2012-12-12T02:08:19.723
9753
2012-12-13T04:17:51.380
2017-04-13T12:43:44.740
-1
706
9751
answer
（１） こわいんです。 means "The thing is... I'm afraid" or "You see... I'm afraid" or
just "I'm afraid!" (you'll translate differently, obviously, if the voice tone
is different).

（２） こわいですから。 expresses the reason explicitly, "kowai desu" + kara. It's polite
(it isn't "kowai kara", kowai has been made polite by desu), but informal (or
you would have said "kowai desu node"). It means "Because I'm afraid...".
Please note the suspension points; the phrase is left in the air, less
assertive and thus it's softer.

（３） こわいからです。 is "kowai kara" + desu, so the reason has been made polite by
desu. It means "Because I'm afraid". It's the neutral way to give a reason,
the one you learn on textbooks. It sounds polite, but assertive (and usually
you want to avoid to be "assertive"), because it ends abruptly and it doesn't
leave space for listener's reply or opinion. Also, for the sake of
completeness, you can't have (×) "kowai node desu".

My first answer here... I hope I've done everything right, and I hope it
helps, obviously^^.
CC BY-SA 3.0
2012-12-12T11:25:31.997
9755
2012-12-12T13:50:25.090
2012-12-12T13:50:25.090
2972
2972
9751
answer