From Daily Writing Tips:
When I received not one, but three emails telling me that I’d punctuated a sentence with because incorrectly, I decided I’d better write a post about adverbial clauses of reason.
Here’s the example that drew the criticism:
Incorrect: The famous author lives in a small town, because she doesn’t like the noise of a big city.
Correct : The famous author lives in a small town because she doesn’t like the noise of a big city.
Here are the objections I received:
1. Number five conflicts with my 11th grade English teacher’s rule. Separate the two halves of a compound sentence with a comma. Was she wrong?
2. I disagree with #5. Two independent clauses should be separated by a comma.”She doesn’t like the noise of the big city.” is an independent clause. Remove the word “because” and you have two sentences that can stand alone.
3. ERROR. “she doesn’t like the noise of a big city” is also an independent clause, and the comma is required. This is a compound sentence with “because” joining two independent clauses.
The readers are perfectly correct about the rule for punctuating a compound sentence. Two independent clauses joined by a coordinating conjunction are separated by a comma:
Polio would have stopped a lesser man, but Franklin was determined to follow his cousin into the White House.
The conjunctions used to join independent clauses in compound sentences are coordinating conjunctions. The most common coordinating conjunctions are: for, and, nor, but, or, yet, and so.
A coordinating conjunction used to join clauses has only one function: it joins clauses of equal importance. Removing the conjunction between two independent clauses will leave two simple sentences whose meanings remain unchanged. They can stand alone as complete sentences.
A subordinating conjunction, on the other hand, has two functions: it joins, and it shows a relationship between the clauses that it joins. Removing a subordinating conjunction defeats the purpose for which it exists.
The subordinating conjunction because is used to introduce an adverbial clause of cause or reason. The fact that the author doesn’t like the noise of the big city explains why she lives in a small town.
Adverbial clauses of reason are also introduced by the subordinating conjunctions since, as long as, as, inasmuch as, insofar as, and due to the fact that.
Reminder: When the adverbial clause comes first in the sentence, it is followed by a comma. When the adverbial clause comes after the independent clause, there is (usually) no need for a comma. For example:
Since you asked nicely, you may go to the library on Saturday.
You may go to the library on Saturday since you asked nicely.
Modern business style tends to reject lengthy conjunctions like inasmuch as and due to the fact that. Because, as, and since are the least wordy choices. Some speakers object to using since to introduce a clause of reason because since is also used to introduce clauses of time. Ordinary attentiveness to revision ought to be sufficient to avoid ambiguity with since.
Link to the rest at Daily Writing Tips