Because, as, since, and commas

Question

From the person who is not a native English speaker, 'because', 'as', and 'since' are the same (or very similar) in that they try give the hints to reason about the main sentence.

From the book that I read, I found that the author uses commas before 'as' and 'since' while he does not use it with 'because'. I also understand that comma is used to give additional information (e.g., My cousin, who has red hair, came late.) while the comma should be removed when the part is necessary to the sense of the sentence (e.g., My cousin who has red hair came late).

Is it common practice that 'since' and 'as' is used with commas while 'because' is not? Or, it just happens that the author uses 'because' with the necessary elements in the book that I read?

Answer 1

This mostly depends on the meaning you're going for.

If you're trying to say that something is the case, and also explain why, then you can use a "because" or "as" or "since" clause that modifies the entire main clause. Because it modifies the entire main clause, it can come either before or after it, and is set off with a comma. So, for example, the following sentences all mean roughly "She wanted a good seat, so she made sure to get there early":

• She made sure to get there early, because she wanted a good seat.
• Because she wanted a good seat, she made sure to get there early.
• She made sure to get there early, as she wanted a good seat.
• As she wanted a good seat, she made sure to get there early.
• She made sure to get there early, since she wanted a good seat.
• Since she wanted a good seat, she made sure to get there early.

But if you're only trying to explain why something is the case, not that it's the case (either because your audience already knows that, or just because it's less important to your point), then you can use a "because" clause that modifies only the predicate. Because it's incorporated into the main clause, it comes at the end, and is not set off with a comma. For example, the following sentence means roughly "The reason I'm here is that I want to be here":

• I'm here because I want to be here.

In this case there will frequently be an explicit contrast between a reason and a non-reason:

• I'm here not because I have to be here, but because I want to be here.

In practice, the line between the two uses of "because" — giving the reason for something that would be expressed anyway, vs. giving the reason for something that's only being expressed in order to give the reason for it — is rather fuzzy. There are many clear-cut cases where only one or the other makes sense, but there are also many cases where either one could work, and it's just a matter of where to place your emphasis.

---

Some additional notes:

• "As" and "since" can also introduce clauses like this that don't modify the whole main clause, but not with the meaning "because". For example, we can say "I got here as she was leaving", meaning "When I got here, she was leaving" (not "I got here because she was leaving"); and "I've known him since I was a child", meaning roughly "I knew him when I was a child, and still do" (not "I've known him because I was a child").
• When the main clause has a negative adverb such as not, the two different uses of because can result in sentences with very different meanings. "I didn't get up to leave, because I was tired" means roughly "I was tired, so I didn't get up to leave"; whereas "I didn't get up to leave because I was tired" means roughly "The reason I got up to leave isn't that I was tired". So in one case the speaker did get up to leave, and in one case the speaker did not get up to leave. This is because of the scope of the because clause: in one case it's part of what's being negated, and in the other case it is not. So the comma can make a big difference sometimes!

Answer 2

While there are some actual rules around the use of commas in English, I feel that many are simple guidelines that illustrate how to use commas to write English with the significant pauses you hear when it is spoken. So, their use is as much personal style as accent or word choice.

Consider my last paragraph, for example. I could have inserted or omitted commas in a variety of spaces including right here but I haven't because it's not required. Or, alternately, I could include a great many weighty, significant commas, since, perhaps, I'd want to break up the sentence into separate thoughts, as if I was talking slowly, or haltingly, or without a clear idea where I was going.

It is important to understand the basic rules for using commas, such as those here. You should certainly study and practice these until they become habit -- but understand that once you get past the basics, it's more about the writer's voice than any inviolable grammar.

Consider this passage from the opening scene in Cormac McCarthy's novel "No Country For Old Men":

When he stood up out of the chair he swung the keys off his belt and opened the locked desk drawer to get the keys to the jail. He was slightly bent over when Chigurh squatted and scooted his manacled hands beneath him to the back of his knees. In the same motion he sat and rocked backward and passed the chain under his feet and then stood instantly and effortlessly. If it looked like a thing he'd practiced many times - it was. He dropped his cuffed hands over the deputy's head and leaped into the air and slammed both knees against the back of the deputy's neck and hauled back on the chain.

Nearly all of McCarthy's writing is like this. Which isn't to say he never uses commas, but he writes as if he's telling you a story in one long string without pausing for breath. That's his signature style, his voice.