What is 〜からです and when is it used? How does it differ from 〜ですから and 〜んです?

Question

I have seen this expression a few times, and have never quite understood it. In particular, it seems to be equatable both to ですから and to んです, but I can't figure out where it would be used over either of those two expressions. Here is an example I found on Google:

新聞{しんぶん}に目{め}を通{とお}していないと、仕事{しごと}が成立{せいりつ}しないからです。

I believe this translates to "Since I haven't been skimming the newspaper, I do not have a job." (but I am not sure, and please correct me if I'm wrong).

What does the からです mean in this sentence? And more importantly, when is it appropriate to use, and how does it differ from ですから and んです?

Answer 1

And more importantly, when is it appropriate to use,

Almost always, although it may sound a little bit informal. When asked "なぜ" or "どうして", you'd answer with からです。

なぜ遅れていますか？

なぜなら、目覚まし時計が壊れていたからです。

(Why are you late? Because my alarm clock is broken)

and how does it differ from ですから　and んです?

ですから is a connective, not a final part. "Aですから、B". If there's no B coming afterwards, then there's a problem. It's a bit like "since" in English. You don't just say "Since I like ice cream," but you say "(B) I bought an ice cream (A) since I like ice cream."

んです is "のです" used more colloquially. It's like からです, and (in "のです" form) more formal. Also more common, as far as I can tell.

Answer 2

Your translation is not correct. It seems that there are a few misunderstandings involved here.

First, “AとB” here means “B if A.” 仕事が成立しない means “I cannot do my job.”

新聞に目を通していないと、仕事が成立しない。 I cannot do my job without skimming the newspaper.

Next, ～から means “because ….” Therefore, your sentence is

新聞に目を通していないと、仕事が成立しないからです。 It is because I cannot do my job without skimming the newspaper.

Note that the whole sentence has the form Xです, where X = 新聞に目を通していないと、仕事が成立しないから. The subject of Xです is not stated, but for example the whole sentence can be a reply to a question “Why do you subscribe to a newspaper?”

As you can see, ～からです is used to state a reason for something.

お菓子を食べたのは、おなかがすいていたからです。 The reason I ate snacks is because I was hungry.

A: どうしてお菓子を食べたのですか。 Why did you eat snacks?
B: おなかがすいていたからです。 Because I was hungry.

In colloquial context, です is often omitted. In this case, we can use polite form before から.

A: どうしてお菓子を食べたのですか。 Why did you eat snacks?
B: おなかがすいていたから。 / おなかがすいていましたから。 Because I was hungry.

If the clause before から is a sentence ending with an adjective or a copula, its polite form ends with です, and you will end up with ですから.

函館山からの夜景を見るといいですよ。とても美しいですから。 You should see the night view from Mt. Hakodate. (This is because) it is very beautiful.

んです does not state that it is a reason. Depending on context, it can sometimes replace からです, though.

A: どうしてお菓子を食べたのですか。 Why did you eat snacks?
B: おなかがすいていたんです。 (Because) I was hungry.

Here おなかがすいていたんです literally just means “I was hungry,” but from the context, it is clear that it is stated as a reason why B ate snacks.