Riddle me this: When you really need one, they’re nowhere to be found, but they pop up when they’re not needed or wanted all the time.
Comma placement is one of the main things I see authors having trouble with. Although there are a number of rules required to get commas right, proper placement is important. Commas signal a short pause in a passage and separate words, clauses, and ideas within a sentence.
This won’t be an extensive look at comma rules, just a quick look at a few rules that will keep your sentences flowing properly.
Independent Clauses
Independent clauses are phrases that can stand alone as independent sentences.
The bus swerved, and I slid out of my seat.
Because this sentence could be broken into two grammatically correct sentences, a comma is required before the conjunction.
The bus swerved.
I slid out of my seat.
Let’s look at another example.
I searched through every DVD in the house, but I couldn’t find anything to watch.
Again, this sentence can be broken into two grammatically correct sentences, which means a comma should be present.
I searched through every DVD in the house.
I couldn’t find anything to watch.
But in this instance, we can rewrite that sentence so it doesn’t require a comma.
I searched through every DVD in the house but couldn’t find anything to watch.
When we remove the subject (I) from the second half of the sentence, it becomes a dependent clause. Now, because the second clause in the sentence is using the same subject as the first, no comma is necessary.
Dependent Clauses
A dependent clause is a phrase that depends on another phrase to form a complete sentence. As in the second example above, a dependent clause at the end of a sentence does not need a comma, but if you’re using a dependent clause at the beginning of a sentence, it must be followed by a comma.
Because the bus swerved, I slid out of my seat.
The clause “because the bus swerved” is not a complete sentence, and since it appears at the beginning of the sentence, it must be followed by a comma.
The same sentence can be rewritten so the dependent clause comes at the end, and eliminates the need for a comma.
I slid out of my seat because the bus swerved.
Both examples above are grammatically correct and switching up the placement of dependent clauses is a great way to vary your sentence structure.
Here’s another example:
Unable to find anything to watch, Lena decided to curl up with a new book.
Again, the clause “unable to find anything to watch” is dependent on the rest of the sentence, and because it appears at the beginning, a comma is required.
Exceptions
As if commas aren’t complicated enough, there are also exceptions. In the case of independent clauses, the Chicago Manual of Style says: “If the clauses are very short and closely connected, the comma may be omitted unless the clauses are part of a series.”
Eric drove and Lena navigated.
Although each part of this sentence is independent, because each clause is so short (two to three words are okay) and closely related, a comma is not necessary. Using a comma in this example wouldn’t be wrong, but could make the sentence choppy.