Deputy Grammar: 12 Laws of the Comma
By: Lindsay Shalla
Tags: Writing, Editing, Grammar, Writing Tips, Comma

Rule #1: Use a Comma with Dependent Clauses and Introductory Words

Words and phrases that begin a sentence are usually separated from the rest of the sentence to promote clarity and avoid misreading. An introductory phrase is also called a dependent clause.

A dependent clause is a sentence that cannot stand on its own. It requires a second sentence to support it because it only has a subject and verb but doesn’t express a complete thought. If you have a dependent clause, use a comma to set it off from the rest of the sentence.

When David gets here, give him the platter of cookies.

If you write a sentence with a dependent clause, in most cases you will use a comma. There are, however, a few circumstances where using one is optional. The first is if you have a three- or four-word phrase that is easily understood.

Once we found it she screamed with glee.

This also applies to sentences that begin with a preposition. A preposition is a word that tells you the location of something in comparison to something else. If the preposition is four words or less, the comma is optional.

Upon the silky cushion he sat.

However, if a dependent clause starting with a preposition contains more than one preposition, you should use a comma. The only exception is if a verb follows directly after the clause ends.

Across the lake and down the hill, the hidden baseball field sits.

Across the lake and down the hill sits the hidden baseball field.

If a sentence begins with an introductory word like namely, i.e., e.g., or for instance and is directly followed by a series of items, a comma can be placed before and after that word, respectively.

There are many options for exercise at the Newfort Gym, namely, running, swimming, and cycling.

Rule #2: Use a Comma with Conjunctions

Confusion presents itself when it comes to commas and conjunctions. Everyone uses conjunctions in their writing. They are the words and, but, or, so, for, nor, and yet. The problem with commas and conjunctions is writers tend to misunderstand where the two should go hand-in-hand.

Commas should precede conjunctions only when the sentences on either side of them are independent. An independent sentence has a subject, verb, and complete thought.

He drove his car to the shop, and he discovered the oil needed changing.

You can omit the comma in sentences that are short and clear.

I run and she skips.

The other exception to this rule is when the subject in the second sentence doesn’t appear before the verb. Only add a comma if the doer of the action is confusing.

The bear growled ferociously and reared up on his hind legs. (The bear does both actions.)

The man cowered as the bear growled ferociously, and cried. (The man cries in this sentence, not the bear, hence the comma.)

Rule #3: Use a Comma to Separate Words or Word Groups in a List

In lists, commas should be used to separate words, word groups, or phrases. Only use a comma if there are more than two words in a list.

On the pizza, include peppers, mushrooms, and olives.

That last comma after the word “mushrooms” is called an Oxford or Serial comma. This comma is used commonly in fiction and other writing in Canada and the US. It is typically not used in newspapers and magazines. You can choose to use it or omit it but be consistent.

However, it must always be used in cases where there is cause for confusion.

Please pack the ice cream, peanut butter and jelly and granola bars. (In this sentence, peanut butter and jelly are grouped together while the rest of the food is not. To show that they are one, add a Serial comma.)

Please pack the ice cream, peanut butter and jelly, and granola bars.

Rule #4: Use a Comma to Separate Coordinate Adjectives

Commas should be used to separate two coordinate adjectives. Coordinate adjectives modify the same noun and can be reversed or interchanged.

The small, scared dog ran underneath the shed.

To determine if you have coordinate adjectives or not, try swapping them to see if the sentence still makes sense. Also, you can put the word “and” between them.

The scared, small dog ran underneath the shed.

The small and scared dog ran underneath the shed.

Rule #5: Use a Comma to Set Off Non-restrictive Items

Some sentences include information that is not essential to the meaning of the sentence. This is considered non-restrictive information. Commas should set off all non-restrictive words, clauses, and phrases. If the non-restrictive information appears mid-sentence, remember to use an appositive comma. An appositive comma is a comma that closes the clause or phrase.

The cat, that is black, jumped onto the sofa.

The four sisters, Luna, Mary, Susan, and Brittany, were tanning on the beach.

Don’t include commas if there is no identified subject in the sentence.

The man with a bald head walked past the hairdresser.

Rule #6: Use a Comma with Direct Quotations

When you use dialogue or a direct quote in your writing, more times than not, it needs to be started or ended with a comma. And the comma needs to be inside of the quotation marks, not outside.

“Today I went to the park,” said Sally.

There are a few exceptions to this rule and they all depend on the format of the sentence. If you have a one-word quotation, the comma can be omitted unless the quotation is followed by a dialogue tag.

Diane yelled “Stop!”

“Stop,” Diane said.

In rare cases, a direct quotation can be the subject or object of the sentence. In this situation, using a comma is optional.

Is “how are you” all you can say to me?

Rule #7: Use a Comma with But and And

Only use a comma before the word “but” if it joins two independent clauses.

Burgers taste delicious, but pizza tastes spectacular.

The same rule applies to the word “and” and commas. Never put a comma before the word “and” if it’s a list of only two items.

Sarah ate her breakfast, and she went out for a walk.

Rule #8: Use a Comma with Names

When directly addressing names, nicknames, terms of endearment, or the title of a person, make sure you set them off with a comma or two.

How are you today, James?

Thank you, Doctor, for telling me.

Baby, you look great!

Rule #9: Use a Comma with Dates

If you include a date in a sentence, commas are required. However, proceed with caution placing the commas because each date format has different rules.

If you write the full date, separate the day of the month and the year with a comma and put a comma after the year.

On October 31, 2008, we had the best Halloween party.

If you write only the month and year or format the date to day-month-year, no comma is required.

I learned how to draw in April 2003.

If your date includes the day of the week as well as the date, separate the day and date with a comma.

On Friday, April 13, I won’t go outside for fear of bad luck.

Rule #10: Use a Comma with Places

When writing a city and its state or country into a sentence, a comma should be used to separate the city and state/country. Also, add one after the state/country to set it off from the rest of the sentence.

I’m going to London, England, in a week.

Rule #11: Use a Comma After Certain Words and Expressions

Some written dialogue will begin with a word such as well, yes, no, hello, or why. Of course, you can use these words in a regular sentence, but you must follow them up with a comma in all situations. If these words are in the middle of a sentence, separate them with commas on both sides.

“Well, I guess I will come.”

I don’t like that, no, I don’t.

Also, use this rule with expressions and words that interrupt the flow of a sentence such as nevertheless, however, after all, by the way, and certainly.

I am, however, terrified.

Rule #12: Use a Comma with Parentheses

Sometimes, information is included in parentheses in the middle of a sentence. Parentheses are used to add in an afterthought or piece of information that is not essential enough to be added with a dash. When putting commas in a sentence with parentheses, the commas should never be placed inside of parentheses. They should only be on the outside and only if there is a need for commas in the main sentence.

After the gun went off, Delilah peeked up and out of the bushes.

After the gun went off (it was a delightful sound), Delilah peeked up and out of the bushes.