One of the biggest editing mistakes found in books involves commas. It is worse when you involve commas and clauses.
The Purpose of Clauses
According to the Webster dictionary, a clause is “a group of words containing a subject and predicate and functioning as a member of a complex or compound sentence.” The purpose of these groups of words is to expand the main part of the sentence. It gives more information to the reader.
Here is an example: As the ball ran out into the street, the dog followed it.
The main part of the sentence is “the dog followed it.” The clause is “as the ball ran out into the street.” The main part can stand on its own. The clause cannot. The clause explains what the dog is following. It supports the main part of the sentence.
An adverbial clause is one that is a big adverb. Instead of one word acting in that capacity, an entire clause is. “Before leaving, Mannie put on his shoes.” The clause “before leaving” is the adverbial clause. It is describing the act of putting on his shoes. A comma has to come after the clause when it is used in the beginning of the sentence. Okay, it doesn’t really have to despite what your teachers say. According to the Chicago Manual of Style, a comma does not have to be used “unless misreading is likely.” (319–6.36) The example of above is one that could be misread. You could say “Before leaving Mannie…” Yes, with the rest of the sentence that wouldn’t make sense, but it would cause a reader to stop and have to read the sentence again to understand what was being said. In that case, put in a comma. I’m one that feels it should be used to be on the safe side.
A dependent clause is one that cannot stand on its own. It is dependent on the main sentence. For example, “If Mary goes to the fair, she’ll have to ride with John.” Unlike the clauses discussed above, these are not adverbs. This one does not explain her actions. It is a clause that explains more of what John is doing. When a dependent clause is used in the beginning of the sentence, as in our example, a comma is used to separate it from the main sentence. But if it was moved to the end of the sentence where it would still make sense, the comma is not needed: “She’ll have to ride with John if Mary goes to the fair.” Unless….
When a dependent clause is mentioned as an aside at the end of a sentence, a comma is used: “She’ll need to ride with you, if you don’t mind.” The clause is not needed. It is said almost as an afterthought and not important to expand the main part of the sentence.
On the other hand, an independent clause is one that can stand by itself. It’s a sentence that is combined with another one. Most independent clauses are combined sentences with ‘but’, ‘and’, or ‘yet’ joining them. When any of these are used to combine independent clauses (or sentences), a comma is used before the conjunction. If an independent clause is used with an independent marker (also, however, therefore, nevertheless), then a semi-colon is used instead of a comma.
A relative clause is one that starts with a pronoun like ‘who’ or ‘that’. They are dependent clauses that are directly related to a noun. These are restrictive clauses. You’ll note that the ‘who’ or ‘that’ can be removed with the sentence still clear to the reader.
The book that Amy is reading is a quick read.
The book Amy is reading is a quick read.
The relative clause here is “that Amy is reading.” If you take that clause out, the sentence makes perfect sense. These clauses do not need commas, but….the nonrestrictive relative clause does. It starts with “which” or “who.”
The book, which I gave Amy, is on the table.
Even this rule is not set in stone and can be acceptable either way. After all, I could say
The book I gave Amy is on the table.
The book that I gave Amy is on the table.
It comes down to the flow of the sentence. When you say “The book, which I gave Amy, is on the table,” you tend to pause more in the reading. That leads us to acceptably put in a comma. When you read the other sentences, it flows smoother with less of a pause if any.
This just scratches the surface. There are so many other situations that could be discussed. We’ll have to save that for later articles.