Common Comma Functions

Commas have many different functions, but their three primary functions are to separate clauses, independent clauses, and they’re used to avoid confusion.

So, since we talked about separating and joining clauses, let’s first talk about what a clause is. A clause is a piece of a sentence.

Mini-test: Common Comma Functions: 

1. Choose the sentence that needs to have one or more commas added:
2.  Choose the version of the sentence that uses commas correctly:


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This transcript is for your convenience.
If you have a dependent clause, it is dependent on the rest of the sentence. It cannot stand alone as a complete sentence, it would be a fragment. If you have an independent clause, it would be able to stand alone as a sentence. It would be independently a sentence on its own. So, dependent clause can’t be a sentence by itself, depends on the rest of the sentence. Independent clause stands alone, can be a sentence all by itself.

So, let’s look at how we can separate clauses with commas.

You only use a comma to separate a dependent introductory clause from an independent clause. So, one way that dependent clauses are used is as an introduction to a sentence.

For instance:

Before the game, Jimmy ate a healthy breakfast.”

We use this comma to separate the dependent clause, so, “before the game” is dependent. You cannot say “before the game” all by itself, and have it be a complete sentence. It’s only a prepositional phrase, so it is a dependent clause.

But then, you have “Jimmy ate a healthy breakfast“. This would be independent. It could stand all by itself. So, you’re separating the dependent introductory clause from the independent clause.

Before the game, Jimmy ate a healthy breakfast.”

And you notice how you pause where that comma is, and a lot of times, that’s why a comma’s there, to get you to pause, so that your sentence makes sense as you’re reading it, either to yourself, in a book, or aloud to someone else. So, a dependent clause as an introduction needs a comma.

Now, let’s look at it if we kind of switch the order of sentence up.

Jimmy ate a healthy breakfast before the game.”

When we put “before the game” at the end of this sentence, we don’t need to have that comma anymore. You only needed the comma whenever we wanted to pause to let people know that “before the game” was separate and to realize the action was happening after that.

So, “Jimmy ate a healthy breakfast before the game“, here, we didn’t actually have to put a comma, because the independent clause came first. So, we had our dependent clause at the end, no comma needed.

That doesn’t mean there will never be a situation where you will have a dependent clause at the end that needs a comma. If you have several items in a series, you may still need a comma toward the end of the sentence, but if you’re using an introductory phrase,  if it comes at the beginning of the sentence, you need the comma, if it comes at the end of a sentence, generally, you won’t. Let’s look at another way that we use commas to separate clauses. You only use a comma to separate two independent clauses joined by any of the following conjunctions – and, a conjunction is basically a connector word – and, but, or, for, nor, so, and yet are common conjunctions. If you have two independent clauses, that means two phrases in a sentence that could stand as a sentence on their own, and they’re connected by one of these conjunctions, then you won’t need a comma to separate those two.

“We are going to the movies, or we are going to a nice restaurant.”

So, here’s our conjunction, “or”. “We are going to the movies” is an independent clause. “We are going to a nice restaurant” is an independent clause. So, the comma is needed to separate two independent clauses. Now, let’s look at if we combine the sentence a different way:

“We are going to the movies or to a nice restaurant.” Here, we have that “or“, so it would be a conjunction, but let’s look.

“We are going to the movies” is an independent clause. “To a nice restaurant” is dependent. “To a nice restaurant” cannot stand by itself. We don’t have a subject in that clause.

And this version of the sentence, we had “We are going” still included, so we still had a subject and a verb, so this was a complete thought all by itself, so it was an independent clause. It could stand as a sentence. “To a nice restaurant” is missing that. It’s missing, well, the subject and the verb, it’s not been made a complete sentence. So, it’s dependent on the rest of the sentence to make sense. So, in this instance, we did not have two independent clauses.  So, no comma was needed. Okay. Now, let’s look at the second primary function of a comma:  to join independent clauses to avoid short, choppy sentences.

So, generally, whenever we are going to join independent clauses, we’re doing it so that we don’t have a series of short, choppy sentences. Now, you’re going to see that this might look a little similar to where we separated independent clauses.

“Sara plays softball, and Sara enjoys swimming.”

Okay. In this one, we had an independent clause, our conjunction, and an independent clause. Let’s look at the next version of this set of clauses.

“Sara plays softball, runs track, and enjoys swimming.” So, “Sara plays softball“, this is independent. “Runs track” is dependent. We have our conjunction, and “enjoys swimming” is dependent, yet, we still have those commas. And then, let’s look at the last version. “Sara plays softball. Sara runs track. Sara enjoys swimming.” So, all three of these are going to be independent clauses, because they are complete sentences,  but they’re short, choppy sentences. “Sara plays softball.”

We keep hearing Sara over and over, and these sentences are short. We can combine them to make it a smoother, flowing sentence. So, you could have two independent clauses joined by a conjunction like we did up here, and then you would use that comma to separate them, but you are still joining multiple sentences when you do that. So, you’re using those commas to separate the clauses, but you were using them to also join two sentences into one.

So, “Sara plays softball, and enjoys swimming.” So, here, we used our comma to join these two independent thoughts.

“Sara plays softball, runs track, and enjoys swimming.” Well, we had dependent clauses here, but we still had a conjunction. The reason we’re going to put commas here is  because you’ve got three or more items in a series. If you list three or more items, or clauses, activities, in a series, you’re going to separate them with commas. So, the reason we’re using it here is to separate three or more items in a series.

Here, we were using it to separate two independent clauses, and then, at the end, we had no commas. We just had three complete sentences, which basically equal three independent clauses.

So, we had to find ways to combine them.  So, we could combine all three into one sentence, and we could use our rule of using three or more commas in a series to join these different independent clauses, or, we could use our rule of separating two independent clauses with a comma and a conjunction, and keep two independent clauses, instead of separating it up and making it dependent clauses, but three different activities in a series. We could say: “Sara collects bananas, apples, and tomatoes.”  We would have to put commas in that series too. “Sara collects bananas” comma “tomatoes” comma, and “apples“. So, when you have three or more items in a series, you have to put your commas to separate them. This is going to be helpful when you’re combining different ideas, to be able to join independent clauses, and in other instances.

If you have just two sentences that you would like to combine, you can do so using a conjunction and a comma, as long as it’s still an independent clause on each side, you will need that comma.

Let’s look at the third primary function of a comma.  They are used to avoid confusion. “I want to eat chicken broccoli and corn for dinner.”

Without a comma in this sentence,  it sounds like you’re saying you want to eat chicken broccoli. Well, you probably don’t know what chicken broccoli is, and that’s because it’s not a real food.

What would make more sense is if we said,  “I wanted to eat chicken” comma “broccoli” comma “and corn for dinner.” Then you would be telling someone you would like to eat chicken, broccoli, and corn. Three items, not chicken broccoli, which makes chicken look like an adjective to broccoli. Now, this comma here, in a series, if you have three or more items, the comma immediately before “and” is optional. Some people like the way it looks, some don’t. I like the way the comma looks, it helps me feel more organized when I’m writing, so I always put it in.

But, you definitely need this comma, because otherwise, the meaning of your sentence is unclear, and you would not be avoiding that confusion.  The commas are supposed to help you avoid.

Let’s look at the next example.

“Before we eat our dog has to eat.”

This doesn’t make sense. “Before we eat our dog.” You’re not going to eat your dog, but if you’re reading this sentence quickly without a comma there to slow you down and make you pause, you don’t read it correctly. You would have to read it a second or third time to get what the author’s meaning actually was.

So, you would say:

“Before we eat, our dog has to eat.”

And maybe this is so that your dog isn’t going to bother you while you eat. If your dog’s already eaten, then you can eat happily. So, “Before we eat, our dog has to eat.” And this is one of those dependent introductory clauses like we talked about up here. We use a comma to separate clauses, and that can also avoid confusion.

So, you see how some of these rules tie in together. Commas in a series, introductory clause being separated from the independent clause that is the rest of the sentence, dependent clause separated from independent clause. So, a lot of the rules of commas may overlap a little bit, but these are three of the primary functions you’re going to see comma’s used for. They’re also used geographically, if you’re talking about a city inside of a country, or inside of the state. If you’re talking about dates or times, then you may also use commas. Commas are used in people’s names sometimes, if you’re putting a Jr. or a Sr.  So, these aren’t the only times you’re going to see commas,  but in writing, these are the primary functions in which you are going to see commas used.

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