"Because" versus "Since" versus "As"

I didn't aware of the difference between "because" and "since" and "as," which can represent reasons as conjunctions.

However, I am sometimes corrected about how to use these conjunctions, so I'd like to summarize the differences of their nuances.

・"Because" is used when the reason is very important, or the reason is new/difficult information.
・"Since" is used when the reason is not important, or the reason is already known.
・"As" is a more casual expression than "since."
・"For" is also used as a conjunction that represents reasons, though, it's a bit old usage.

Since there are no clear rules about using these conjunctions, maybe no need to become nervous.

However, if we used "because" for a matter of course, it would sound as if mocking.

For example, "because it raining, it is humid."

I'd like to be careful.

私はこれまで、理由を表すことができる接続詞 "because" と "since" と "as" の違いをあまり意識してきませんでした。

しかし、何度かこれらの使い方を添削されることがあったので、ニュアンスの違いを調べてまとめてみました。

・"Because" は、理由が重要なときや、理由が新しい情報であるとき、あるいは難しいことを説明するときに使われる。
・"Since" は、理由が重要ではないときや、理由が既に知られているときに使われる。
・"As" は、"since" よりも砕けた表現。
・古い用法だが、"for" が理由を表す接続詞として使われることもある。

厳密な使い分けのルールは無いようなので、そんなに神経質にならなくてもよさそうですが、当たり前のことに "because" を使うと相手をバカにしたように聞こえるみたいです。

例：雨が降っているから、湿気が多い。

注意したいです。

• Since there are no clear rules about using these conjunctions, maybe no need to become nervous.
• Since there are no clear rules about using these conjunctions, then maybe there is no need to become nervous.

• For example, "because it raining, it is humid."
• For example, "because it's raining, it is humid."

Interesting!

• I didn't aware of the difference between "because" and "since" and "as," which can represent reasons as conjunctions.
• I wasn't aware of the difference between "because" and "since" and "as," which can represent reasons as conjunctions.

• However, I am sometimes corrected about how to use these conjunctions, so I'd like to summarize the differences of their nuances.
• This sentence is perfect! No correction needed!

• ・"Because" is used when the reason is very important, or the reason is new/difficult information.
• This sentence is perfect! No correction needed!

• ・"Since" is used when the reason is not important, or the reason is already known.
• This sentence is perfect! No correction needed!

• ・"As" is a more casual expression than "since."
• This sentence is perfect! No correction needed!

• ・"For" is also used as a conjunction that represents reasons, though, it's a bit old usage.
• This sentence is perfect! No correction needed!

• However, if we used "because" for a matter of course, it would sound as if mocking.
• However, if we used "because" for a matter of course, it would sound as if we were mocking.

• For example, "because it raining, it is humid."
• For example, "because it is raining, it is humid."

• I'd like to be careful.
• This sentence is perfect! No correction needed!

• I didn't aware of the difference between "because" and "since" and "as," which can represent reasons as conjunctions.
• I wasn't aware of the differences between "because" and "since" and "as," which are conjunctions that connect results and reasons.

  Note: The last part is not a commonly used phrase at all! But I think the way I've formulated it is the way a native speaker would express this rather abstract idea. However, I get the feeling that however you express this idea, unless your listener is very sharp, you're going to have to explain what you mean in more detail anyway :)

• However, I am sometimes corrected about how to use these conjunctions, so I'd like to summarize the differences of their nuances.
• This sentence is perfect! No correction needed!

• ・"Because" is used when the reason is very important, or the reason is new/difficult information.
• This sentence is perfect! No correction needed!

• ・"Since" is used when the reason is not important, or the reason is already known.
• This sentence is perfect! No correction needed!

• ・"As" is a more casual expression than "since."
• This sentence is perfect! No correction needed!

• ・"For" is also used as a conjunction that represents reasons, though, it's a bit old usage.
• ・"For" is also used as a conjunction that represents reasons, although its usage is a bit old-fashioned.

  or: "though its usage is a bit old-fashioned." "Old" might work, too, but "old-fashioned" or "antiquated" are more specific and a little better.

• Since there are no clear rules about using these conjunctions, maybe no need to become nervous.
• Since there are no clear rules about using these conjunctions, there's probably no need to be nervous about their usage.

  The other correction is good too, but I've written in it in a way that feels natural to me. A note: Although it's understandable, I would not use "become" here. I would always use "be." It's interesting that in the Japanese translation, this is not the case: "...神経質にならなくて..."!

• However, if we used "because" for a matter of course, it would sound as if mocking.
• However, if we used "because" for ordinary matters, (it would sound as though we were using it mockingly) / (it would sound as though we were mocking the person we were speaking to). (第二目はkanotownさんの日本語翻訳から）

  Hmmm... "matter of course" is not such a commonly heard phrase. I changed it to how I would translate your Japanese version, but by all means keep using "matter of course!" It's nice to be better than a native speaker :)

• I'd like to be careful.
• This sentence is perfect! No correction needed!

Interesting! I'll just say that I don't find anything mocking about the sentence "Because it is raining, it is humid." Maybe if it were used in a negative context, I might feel that way... for example:

Me: It sure is humid today.
Friend: It's humid because it's raining, you idiot.

That would be mocking and insincere! But it would be just as mean for my friend to say:

It's humid since it's raining, you idiot.

(Actually, to me, to use the word "since" sounds slightly strange to me; I'd only use "because.")

Anyway, the point is, don't worry about offending people because you use the wrong word!