20 Commas

I’ll admit it right at the start of this chapter: I love commas. I think they’re great, and I use them more often than other people because I find them helpful as a reader. Commas help readers navigate sentences by separating and organizing various parts of a sentence visually. Commas can also determine and change the meaning of the words around them, so it’s important to know how to use them properly.

Commas change

IMAGE – LET’S EAT GRANDPA!

to

IMAGE – LET’S EAT, GRANDPA!

Commas can even cost you money (okay, probably not you, but they have cost at least one business millions of dollars).

There are a lot of rules about commas, and they can be intimidating. But I want you to be confident in your commas, so let’s start by employing our own experience as readers and speakers to decide where commas go.

You Know More Than You Think

First, we encounter commas all the time as readers, and all that experience has given us a pretty good idea where they go. So if you just go on instinct alone, you’ll probably be pretty accurate.

Second, we know what sentences sound like. If a comma is usually matched with a pause, then we can read sentences out loud and place commas where the pauses are.

I hope at this point that you’ve developed some confidence in your natural understanding of commas, but the best way to be confident in their use is still an awareness and understanding of a few basic comma rules.

And Now, Some Rules

Below I’m going to share five basic comma rules. There are plenty more out there, but these are the ones most important for the work we’re doing in this class.

Rule 1: Lists

This rule is pretty simple: add commas between items in a list when there are three or more items.

On the way to school I saw a mouse, a cat, and a raccoon.

There are three items in the list (mouse, cat, raccoon), so I make sure to place a comma between each.

On the way to school I saw a mouse and a cat.

In this sentence, there are only two items in the list (mouse, cat) so I shouldn’t use any commas.

Rule 2: Coordinating Conjunctions

Use a comma before a coordinating conjunction (aka, a FANBOYS word) when the conjunction is being used to connect two independent clauses.

The turkey ran across the road, and I was the only one who saw it.

Here I’m using the coordinating conjunction and to connect two independent clauses (two groups of words that could be sentences on their own). I place a comma before the conjunction to show that I’m using it for this special purpose.

I enjoyed the film but hated the popcorn you made.

Here I’ve used a coordinating conjunction but. However, I’m not using it to connect two independent clauses; instead, I’m using it to connect two phrases (enjoyed the film, hated the popcorn). Because I’m not using the conjunction to connect independent clauses, I should leave out the comma.

Rule 3: Introductory Material

Place a comma after introductory words, phrases, and clauses in a sentence. These parts of a sentence set up the main idea, but they’re not part of the main idea. Let’s see some examples:

However, I did not steal your pen.

• • • introductory word

At night, raccoons search for food.

• • • introductory phrase

Because you didn’t pay your fees, we have cancelled your membership.

• • • introductory dependent clause

The challenge with this rule is determining where the introductory information ends. Notice, though, that in each of the sentences above, the subject appears right after the comma. So, if you see introductory information, find the subject and place the comma in front of it.

Rule 4: Interrupters and Appositives

Sometimes, as a writer, you’ll feel the need to add some additional, but not vital, information in the middle of a sentence. In fact, I just did so twice in that last sentence. We’ll call those bits of extra information interrupters (they are also known as parenthetical statements). When you add interrupters to a sentence, you should surround them with commas — like this:

The kids’ teacher, a person very close to retirement, was often impatient with them.

These commas are a more formal alternative to parentheses (curved brackets) or dashes, which could also be placed in the same spot in more casual contexts like workplace communication.

The kids’ teacher (a person very close to retirement) was often impatient with them.

The kids’ teacher — a person very close to retirement — was often impatient with them.

In all of these cases, the punctuation indicates that the part that has been surrounded is not part of the main idea of the sentence — it’s extra.

Rule 5: Non-Essential Clauses

Most of the time, when you want to describe something you use a word or a phrase. But sometimes the best way to describe something within a sentence is to use a clause, like I’ve done here:

The SUV that I bought last week already had a flat tire.

My new SUV, which I bought last week, already had a flat tire.

Those underlined clauses (called a relative clause) provide more information about the SUV I mentioned at the beginning of the sentence. Notice, though, that in one sentence the clause is surrounded by commas, just like we did in Rule 4, but the other sentence doesn’t use commas at all. So how do you decide whether to add commas?

To decide whether to add commas, we need to determine whether the clause is essential. By essential I mean that it needs to be there; without it, readers won’t be able to identify which specific SUV I’m talking about. Let’s examine the sentences again:

The SUV that I bought last week already had a flat tire.

• • • The clause in this sentence is necessary because it confirms that I’m talking about a specific SUV — mine.
    • Because the information is essential, we don’t put any commas around it.

My new SUV, which I bought last week, already had a flat tire.

• • • The clause here doesn’t help us identify which SUV I’m talking about; I already provided that information by using the words “My new.”
    • Because the information is non-essential, we put commas around it. We basically treat it like an interrupter.