The Comma

It’s easy to understand why some people rely on the old adage “use a comma when you need to pause” because the comma has so many uses, but that so-called “rule” tends to be hit and miss.

For example, take a look at the following sentence.

Standard
The deplorable working conditions in all three of our branch offices must be changed immediately.

Since the sentence has such a long subject phrase (“The deplorable working conditions in all three of our branch offices”), the tendency is to pause before moving on to the verb phrase (“must be changed”), but there is no grammatical reason for putting a comma there.

By contrast, read this sentence:

Standard
Without bacon, even the best BLT isn’t the same.

Some readers will read that sentence with a pause after “bacon,” but others will not. Since different readers will feel the need to pause or to avoid pausing at different points in the same sentence, there can be no consistency to such a plan.

Although it would be nice to have only one rule to follow, the comma has too many functions and is too complex to be governed by one overarching rule. This guide, following the order and numbering system of Guide to Rapid Revision (Pearlman and Pearlman 40–46), contains six basic comma rules.

Conjunction is just a fancy way to say “linking word” or “connecting word.” Coordinating is a fancy way of saying that this type of connecting word connects equivalent things—in this case independent clauses, not dependent clauses. The coordinating conjunctions in English are for, and, nor, but, or, yet, and so. One way to remember these is the acronym FANBOYS. Let’s take a look at this rule in general; after doing so, we’ll cover an example of each coordinating conjunction, one at a time, addressing the possible confusions that relate to each.

Look at the following three examples:

Standard

A. She went to the baseball game. It was cancelled because of rain.

B. She went to the baseball game; it was cancelled because of rain.

C. She went to the baseball game, but it was cancelled because of rain.

Each example shows a standard way to express the information. Each one consists of two independent clauses, but each one deals with the two in a different way. Example A presents the two independent clauses as two separate sentences. Example B connects the two independent clauses with a semicolon; as we’ve seen, that is an appropriate use of the semicolon. Example C connects the two independent clauses with both a comma and a coordinating conjunction.

Now look at the following nonstandard examples:

Nonstandard

A. She went to the baseball game it was cancelled because of rain.

B. She went to the baseball game; but it was cancelled because of rain.

C. She went to the baseball game, it was cancelled because of rain.

D. She went to the baseball game but it was cancelled because of rain.

All of these are nonstandard because they fail to follow our first comma rule. Example A provides nothing but a space between the two independent clauses. This is an error called a fused sentence, which is also known as a run-on sentence, and we’ll address it again in the section titled “Sentence Correctness.”

Example B connects the two independent clauses with a semicolon and a coordinating conjunction, making it technically incorrect. Using a semicolon, an adverbial (rather than coordinating) conjunction, and a comma (for example, “She went to the baseball game; however, it was cancelled because of rain”) would be standard, but using a semicolon and a coordinating conjunction is not.

Example C connects the two independent clauses with a comma alone. This is an error known as a comma splice, and it will be addressed later in this section.

Example D connects the two independent clauses with a coordinating conjunction alone.

In order to connect two independent clauses correctly, both a comma and a coordinating conjunction must be used.

Now let’s take a look at how this rule plays out in each of the coordinating conjunctions in English (the FANBOYS).

For

Standard

I would like to go to the party tonight, for I think Trevor is a nice guy.

Avoid confusing the use of for as a preposition, a word that can connect nouns to the rest of a sentence, and for as a coordinating conjunction. In the following sentence, for is a preposition, and no comma is needed before it.

Standard

I would like to go to the party tonight for the good appetizers.

And

Standard

She was intelligent, and he was charming.

In the sentence above you see the more commonly used coordinating conjunction and between two independent clauses. However, what about the following nonstandard sentence?

Nonstandard

She was intelligent, and was impressed by his charm.

There should not be a comma before and in the nonstandard sentence because it is not linking two independent clauses with both a subject and a verb. There is no subject inserted after and. Instead, the conjunction and is being used to connect the two verb constructions “was intelligent” and “was impressed by his charm,” thus not requiring a comma.

Nor

Standard

I will not attend the performance on Thursday, nor will I attend the Saturday matinee.

Nor is a word that, when used with independent clauses, may have a formal-sounding sentence structure. The second independent clause has a structure where part of the verb (“will”) appears before the subject. Nonetheless, this is a standard construction.

You’re more likely to use nor when nouns instead of whole clauses are connected.

Standard

Neither Mackenzie nor Maria will attend the play.

In such constructions, a comma does not precede the nor.

But

Here’s a coordinating conjunction that's used a lot.

Standard

I read Shakespeare’s Hamlet, but I enjoyed Macbeth more.

Be careful to avoid using a comma when it’s not separating two independent clauses as in the following nonstandard example.

Nonstandard

I read Shakespeare’s Hamlet, but enjoyed Macbeth more.

Standard

I read Shakespeare’s Hamlet but enjoyed Macbeth more.

You don’t need a comma in that sentence since the subject “I” is not inserted again into the second potential clause before “enjoyed.”

Or

Another common coordinating conjunction is or.

Standard

Leave the building at once, or I will have to call security.

The comma is standard for the two independent clauses. You know that the first one is an independent clause because it is written like a command with you as the understood subject.

The comma is nonstandard in the following sentence since no second subject is inserted before the second verb.

Nonstandard

I need to decide whether I should fish, or cut bait.

Yet

Standard

He was intrigued by the mysterious offer, yet he was wary.

As with the previous examples, avoid inserting a comma before yet when it’s not followed by another subject and verb (another independent clause, in other words).

Standard

He was intrigued yet wary about the mysterious offer.

So

Last but not least, we have so, which presents a new challenge. Examine the two sentences below.

Standard Sentences

Delaney eats protein every morning, so he buys eggs and low-carb granola bars.

Delaney woke up early every day to practice so he would make finals.

There are definitely two clauses in each sentence, the second clause in each beginning with “so” followed by the subject “he.” However, the second sentence is standard without a comma, unlike the first sentence. How can that be?

In the first sentence, “so” is a coordinating conjunction separating two independent clauses, but in the second sentence, something has been omitted from the sentence. “So” stands for the subordinating conjunction so that.

If a coordinating conjunction connects equal parts of a sentence, a subordinating conjunction connects an independent clause with a dependent one, a subordinate one. In fact, what subordinates the clause is the subordinating conjunction. In the sentence below, so that makes “he would make finals” dependent on the clause before, not an equal clause.

Standard

Delaney woke up early every day to practice so that he would make finals.

When it comes to commas and two apparent independent clauses separated by a so, test to see if you can insert the word that after so. If you can, you do not need a comma.

You can also try a second test. Try replacing so with the more common coordinating conjunction and. If and makes sense, the so in the sentence is probably also a coordinating conjunction.

Standard

Delaney eats protein every morning, and he buys eggs and low-carb granola bars.

Nonstandard

Delaney woke up early every day to practice and he would make finals.

For the Careful Writer:

Avoid doubling coordinating conjunctions: “and so” is more clearly expressed as either “and” or “so”; “but yet” is more clearly expressed as either “but” or “yet.”

Students are sometimes taught that they should never begin a sentence with a conjunction. But that idea does not have any grammatical rationale. If you do begin a sentence with a conjunction, note that it should not be followed by a comma (unless some other grammatical reason compels the use of a comma there).  This is a particularly pernicious error with so, and it may spring from the idea that so can mean therefore or thus.  Instead of “So, we must pay attention to our use of coordinating conjunctions” write either “So we must pay attention to our use of coordinating conjunctions” or (even better) “Therefore, we must pay attention to our use of coordinating conjunctions.”

Nonstandard Sentences

But, she never realized that the bicycle had been painted blue.

And, I didn’t have the extra five dollars for the ticket.

Standard Sentences

But she never realized that the bicycle had been painted blue.

And I didn’t have the extra five dollars for the ticket.

An introductory phrase is a phrase that comes before the main clause of the sentence.  In the standard sentences below, the main clauses are “I stayed up late writing this” and “I headed for bed.” The “Knowing” and “After” phrases come before those main clauses, so they are followed by commas.

Standard Sentences

Knowing that I needed to finish before dawn, I stayed up late writing this.

After I managed to finish, I headed for bed.

This rule also applies to transitional words and phrases such as those in the following list.

Following this rule, the comma also sets off opening interjections, which are short, often emotion-laden words that frequently can stand by themselves.

Standard Sentences

Wow, that coffee is hot.

No, I didn’t bring enough coffee for the whole class.

If you have multiple opening interjections, set each one off with a comma.

Standard Sentences

Hi, Joe, I’m glad to see you.

Hello, sir, let me take your coat.

Oh, yes, Molly, I think it is.

Note: The Chicago Manual of Style says, “Although an introductory adverbial phrase can usually be followed by a comma, it need not be unless misreading is likely. Shorter adverbial phrases are less likely to merit a comma than longer ones” (6.31). If there is any doubt about whether your readers will understand you, use a comma after an introductory word or phrase.

Notice in the sentence below that you could easily cross out “the queen of Tennessee cities” and still understand the meaning of the sentence perfectly well. 

Standard

Chattanooga, the queen of Tennessee cities, has over 150,000 residents.

A nonrestrictive phrase (also known as a parenthetical phrase) can be removed from a sentence without changing the essential meaning of the sentence. It’s called nonrestrictive because it doesn’t restrict the meaning. In the rest of the sentences below, the phrase that is set off by commas could be removed from the sentence without altering its essential meaning.

Standard Sentences with Nonrestrictive Phrases

Stealing a policeman’s helmet, a crime of which Bertie Wooster stands accused, is too common a misdemeanor.

The lake, which freezes over every January, is warm enough for swimming.

Note that commas do not set off restrictive phrases. A restrictive phrase cannot be removed from a sentence without changing its essential meaning: such a phrase restricts the meaning of some part of the sentence. In the sentences below, the phrases “that is on the left,” “except Marlowe,” and “who is lecturing on Shakespeare” are not set off by commas because removing them would change the essential meaning of the sentence.

Standard Sentences with Restrictive Phrases

The lake that is on the left is warm enough for swimming.

Everyone except Marlowe was rewarded.

Of the two professors, the one who is lecturing on Shakespeare is seated.

Scientists who believe that the moon is made of cheese often get hungry during astronomy class.

On “Which” and “That” Phrases

The general rule in standard American edited English (British use is different) for the use of phrases beginning with “which” or “that” is that “which” is used for non-restrictive causes and “that” is used for non-restrictive clauses.

Standard Sentences with “which” and “that” Phrases

Potato chips that have less salt are better for you.

Potato chips, which are my favorite snack, are not completely healthy.

I want to work on a musical that combines space flight and bluegrass standards.

I want to work on a musical, which is also your goal.

Commas also precede -ing participial phrases that follow the main clause.

Standard Sentences with Nonrestrictive -ing Phrases (participial phrases)

Cassius begins the conversation, marveling at the fame that is now theirs for all time.

She has seen seventeen operas this year, not counting the ones she directed.

We rode in a one-horse open sleigh, dashing all the way.

For most formal writing, it is always wiser to use the last comma in the series (the comma called the Oxford comma or the serial comma). Insert a comma before the conjunction and after the second-to-last item in the list.

Standard Sentences

There are many examples above, below, and to the right of this sentence.

Please buy me some salt, some sugar, two lemons, and six limes.

Do you have any extra books, paper, or pencils?

Put away your cell phone, pager, and bagel.

Take a look at the sentence below.

Standard

It is a cold, gray day.

Remember that one way to identify most nouns is if they are preceded (or could be preceded) by a, an, or the. In this case, the “a” precedes the noun “day” and two adjectives describing day: “cold” and “gray.” Remember that the word coordinate means equal in importance. When two adjectives like these before a noun are equal in importance, you insert a comma between them. There are a couple ways to test if they’re equal in importance.

A. The comma could be replaced with the word and without changing the meaning.

Standard

It is a cold and gray day.

B. The two words could be reversed without changing the essential meaning.

Standard

It is a gray, cold day.

You know that the two adjectives are not coordinate when neither of the tests works. Examine the sentence below.

Standard

She was an overworked administrative assistant.

Here “overworked” is describing not just “assistant” but “administrative assistant.” Thus, no commas are needed. The tests listed as A and B above confirm this:

Nonstandard

She was an overworked and administrative assistant.

Nonstandard

She was an administrative, overworked assistant.

In both these tests, the resulting sentence is unclear and awkward, showing that “overworked” and “administrative” are not equal in importance.

Here are other examples of coordinate adjectives italicized below.

Standard Sentences

My teacher was an eccentric, colorful lady.

He had a wild, haunted look.

By then, he was an old, old dog.

The five rules above cover the primary uses of the comma. This rule addresses common misuses of the comma. We will learn how to avoid adding needless commas.

Nonstandard

The crazy relationship that they had, puzzled all onlookers.

Standard

The crazy relationship that they had puzzled all onlookers.

There’s an uninformed tendency to insert a comma if the subject is long.

A comma does not set off restrictive phrases.

Nonstandard

A man, who was having chest pains, was first priority at the Emergency Room.

Standard

A man who was having chest pains was first priority at the Emergency Room.

The phrase “who was having chest pains” is restrictive (thus, no comma) because it explains why he was first priority at the Emergency Room. 

A comma does not appear after the last item in a list unless some other grammatical reason compels it to do so.

Nonstandard

The fight, the spat, and the scuffle, caused tension in their relationship.

Standard

The fight, the spat, and the scuffle caused tension in their relationship.

Nonstandard

She went to see the play, the opera, and the film, when she learned that there were three other versions of her favorite novel.

Standard

She went to see the play, the opera, and the film when she learned that there were three other versions of her favorite novel.

However, if the end phrase of the last nonstandard sentence started with –ing (if it were an -ing participial phrase following the main clause, in other words), a
comma before it would be standard:

Standard

She went to see the play, the opera, and the film, having learned that there were three other versions of her favorite novel.

A comma does not separate a dependent clause from an independent clause.

Nonstandard

They went to the market, and found that they couldn’t buy anything.

Standard

They went to the market and found that they couldn’t buy anything.

For the second part of the sentence, you need to insert a subject before the verb “found” for the sentence to require a comma to separate two independent clauses.

Standard

They went to the market, and they found that they couldn’t buy anything.

A comma does not precede a subordinate phrase that comes after the sentence’s main phrase.

Nonstandard

She wanted to go to the baseball game, because he wanted to see a Shakespeare play.

Standard

She wanted to go to the baseball game because he wanted to see a Shakespeare play.

Nonstandard

She will go see the Shakespeare play, even though the Twins are playing the Cardinals. 

Standard

She will go see the Shakespeare play even though the Twins are playing the Cardinals.

A comma does not join two independent clauses without a coordinating conjunction. Such an error is called the comma splice.

Nonstandard: Comma Splice

She wanted to go to the baseball game, he wanted to see a Shakespeare play.

Standard Sentences: Avoiding the Comma Splice

She wanted to go to the baseball game, but he wanted to see a Shakespeare play.

She wanted to go to the baseball game; he wanted to see a Shakespeare play.

She wanted to go to the baseball game. He wanted to see a Shakespeare play.

She wanted to go to the baseball game even though he wanted to see a Shakespeare play.

She wanted to go to the baseball game; however, he wanted to see a Shakespeare play.

For the Careful Writer:

A comma called “the thousands separator” is used to separate thousands (e.g., one thousand, a thousand thousand, a thousand thousand thousand) when writing numbers.

Standard

She said that she has told me not to wear a bow tie 1,302 times.

I cried 9,999,999 tears over you. [Note: That is an allusion to the song “9,999,999 Tears” performed by Dickey Lee in 1976.]

Please pay me the $12,288 you owe me.

While we’re at it, you owe me some change as well. I’ll just use a decimal separator to tell you that you owe me $12,288.42.