In Part 1 of my blog series on comma usage, we looked at some of the basic comma rules. In Part 2, we’re going to cover the more intricate comma rules that show up in sentences. How much fun could we possibly have in two blogs?!
This is the trickiest arena in which to learn comma usage. You really need to know the rest of your grammar rules well in order to properly use commas. Knowing dependent and independent clauses is essential – so bone up on it if you must! (These videos are a good place to start.) In today’s post, I’m going to cover each of the four sentence structure types and let you know when and when not to use a comma.
1. Comma Rules for Compound Sentences
When you have two independent clauses (i.e., full sentences) that are joined by a coordinating conjunction, you have a compound sentence.
Most of the time you are going to use or, and, or but as coordinating conjunctions; however, there are others like so, yet, and for.
Do use a comma in front of the coordinating conjunction when it joins two independent clauses.
They enjoyed their trip, and they hope to go back again soon.
I have no idea where they went, but I would be happy to help you find them.
Don’t include a comma when you have two short independent clauses that are closely related. (This is an exception to the rule above.)
- We went to the market and Dad bought apples.
2. Comma Rules for Complex Sentences
In a complex sentence, you have an independent clause and at least one dependent clause. An independent clause can stand on its own, but a dependent clause wouldn’t make sense on its own as a sentence. You will usually find the dependent clause starts with a conjunction or preposition like although, since, and while.
Dependent before Independent
Let’s look at dependent clauses that come before independent clauses.
If the dependent clause precedes the independent clause, do separate it with a comma.
Although we enjoyed the show, the popcorn was inedible.
While we waited for Mike, Sarah went to freshen up her makeup.
Now, if you have two dependent clauses before the independent clause, don’t separate the two dependent clauses with a comma. You only use a comma after the second dependent clause.
- Since you’ve been gone so long and spent too much money, we’ve decided to sell all your furniture.
Independent before Dependent
Don’t use a comma if you have an independent clause before a dependent clause. So, building on the examples above:
- We’ve decided to sell all of your furniture since you’ve been gone so long.
Sarah went to freshen up her makeup while we waited for Mike.
The exception to the above rule about independent clauses preceding the dependent clause is in cases where the dependent clause is not essential to the meaning of the entire sentence. It’s almost like an afterthought. In cases like this, do separate the dependent clause with a comma.
- The four-hour opera was well received, if you like that sort of thing.
In the above sentence, liking opera has nothing to do with how well it was received by the general audience. Therefore, you should set the dependent clause apart with a comma.
Dependent in the Middle
If the dependent clause falls in the middle of the sentence AND that clause is not essential to the sentence, then do set it off with commas.
The bridegroom, who was wearing a tuxedo, could not figure out where the reception hall was located.
In the above sentence, the fact that the bridegroom was wearing a tux has no relevance to why he couldn’t find the reception hall, and is not essential to the sentence.
If the dependent clause falls in the middle of the sentence AND is essential to the meaning of the sentence, don’t set it off with commas.
The bridegroom who took a blow to the head could not figure out where the reception hall was located.
Here the poor bridegroom’s blow to the head has everything to do with not being able to figure out the location of the reception hall. Therefore, the commas need to be omitted.
3. Comma Usage in Compound-Complex Sentences
As the name suggests, a compound-complex sentence is a combination of two or more independent clauses along with at least one dependent clause. So it looks like this:
Compound-Complex Sentence =
- independent clause +
- independent clause +
- (at least one) dependent clause
The clauses can be in any order as per below.
Dependent Preceding Two Independent
When you have a dependent clause followed by more than one independent clause, do place a comma after the dependent clause. Don’t place a comma between the two independent clauses.
When we go to the movies, you get the popcorn and I’ll grab some candy.
Dependent Between Two Independent
When you have a dependent clause that occurs in the middle of the sentence, do set it off with commas.
The couple was in love, and when Bobby proposed, Sarah immediately said yes.
4. Comma Usage in Simple Sentences
In a simple sentence, you only have one independent clause. Now, you may have a conjunction within that sentence where you are really itching to put a comma. Don’t do it! Fight the urge and let the sentence stand without the comma.
Don’t put a comma to separate the subject from the verb in a simple sentence, even if it feels like there should be a pause.
The toughest thing about using commas is knowing where to use them.
It would be tempting to put a comma after the word commas. Don’t do it.
Don’t use a comma in a simple sentence, even if the sentence contains a conjunction.
Larry drove to Long Island but didn’t stay overnight.
Sherry watched the game from the skybox and loved it.
The exception to the simple sentence rule is if omitting the comma will make the sentence confusing. If that’s the case, by all means, do put the comma back in.
Grapes are as good for you as bananas, and apples even more so.
If you have a compound subject or compound object in a sentence, don’t separate them with a comma.
- Jerry, and the rest of the gang will be here tonight.
Jerry and the rest of the gang will be here tonight.
If you have a compound predicate, don’t separate it with a comma.
- My spirit was willing to go the extra mile, but my body wasn’t.
- My spirit was willing to go the extra mile but my body wasn’t.
The exception to the compound predicate rule is if it will be confusing to the reader without the comma. If it is confusing, do include the comma.
- They saw the arrest of the felon who robbed the bank and smiled.
- They saw the arrest of the felon who robbed the bank, and smiled.
Adding the comma shows the intent of the sentence is the fact that “they” are the ones smiling, not the felon.
Comma Rules at War
So, let’s say you are using all of these comma rules in your writing. But what happens when you look at a sentence you have just written and it has almost as many commas as it does words? Then what?
- I made it to the movies, and, if I were to be honest, it wasn’t worth the trip.
In the above sentence, all of the rules were followed. But now we’ve got a boatload of commas. What to do, what to do?
There is no singular agreement on what to do with all of the commas, except to lighten up on them.
- Option A: You could eliminate the comma rule before the word and.
I made it to the movies and, if I were to be honest, it wasn’t worth the trip.
- Option B: You could remove the comma before the dependent clause.
I made it to the movies, and if I were to be honest, it wasn’t worth the trip.
- Option C: You could be daring and just use a semicolon to eliminate the pesky conjunction and all together.
I made it to the movies; if I were to be honest, it wasn’t worth the trip.
Quick note for Option C: Another good way of writing that sentence would be to use the semicolon, but change the conjunction from and to but.
I made it to the movies; but if I were to be honest, it wasn’t worth the trip.
I wanted to point this out for two reasons. First, I personally think that this version of the sentence works the best! Second, I wanted to point out another comma rule.
Most writers would put a comma after the word but. DON’T! This is a very frequent mistake and results in overuse of commas. People seem to think that conjunctions automatically need a comma, but they do not. As you can see, the sentence written without a comma reads very well! And it is correct!
So after semicolons, you don’t always have to insert a comma when you have a transitional conjunction.
Whew! I’m out of breath, and you are very likely sick to death of reading about commas!
That’s OK. Just bookmark this page (as well as our Professional Writing lessons), and you will have these tips at your fingertips whenever you are writing and have a question about whether or not to use our little friend – the comma!