Ah, the comma. Of all the punctuation marks in English, this one is perhaps the most misused. And it’s no wonder. There are lots of rules about comma usage, and often the factors that determine whether you should use one are quite subtle. But fear not! Below, you’ll find guidance for the trickiest comma questions.
What is a comma?
While a period ends a sentence, a comma indicates a smaller break. Some writers think of a comma as a soft pause—a punctuation mark that separates words, clauses, or ideas within a sentence.
When to use commas
Commas have quite a few uses in English:
- Separating items in a list of three or more
- Connecting two independent clauses with a coordinating conjunction
- Setting apart non-restrictive relative clauses
- Setting apart nonessential appositives
- Setting apart introductory phrases
- Setting apart interrupters and parenthetical elements
- Setting apart question tags
- Setting apart names in direct address
- Separating parts of a date
- Separating parts of a location, like a city and its country
- Separating multiple coordinating adjectives
- Separating quotations and attributive tags
There are a lot of technical English words in that list, but don’t worry. We explain everything in detail below.
Commas with lists
When you have a list that contains more than two elements, use commas to separate them.
(The comma before the and in a list of three or more items is optional. See below, under “Serial comma,” for more information.)
Your list might be made up of nouns, as in the example above, but it could also be made up of verbs, adjectives, or clauses. Imagine, for a moment, that you have just finished doing three chores. The chores were:
- Cleaning the house and garage
- Raking the lawn
- Taking out the garbage
If you were to list these three chores in a sentence, you would write:
I cleaned the house and garage, raked the lawn, and took out the garbage.
or
I cleaned the house and garage, raked the lawn and took out the garbage.
Serial comma (Oxford comma)
As mentioned above, when you are listing three or more items, commas should separate each element of the list. However, the final comma—the one that comes before the and—is optional. This comma is called the serial comma or the Oxford comma.
Whether or not you use the serial comma is a style choice. Many newspapers do not use it. Many trade books do use it. In your own writing, you can decide for yourself whether to use it—just be consistent.
Keep in mind, though, that occasionally the serial comma is necessary for clarity.
I dedicate this award to my parents, Jane Austen and Albert Einstein.
The sentence above will almost certainly cause readers to do a double take. Without a serial comma, it looks like “Jane Austen and Albert Einstein” is an appositive, rather than the second and third elements in a list. To put it another way, the writer seems to be saying that her parents are Jane Austen and Albert Einstein. A serial comma eliminates the possibility of misreading, so even if you’re not using serial commas in your writing, make an exception for sentences like this:
I dedicate this award to my parents, Jane Austen, and Albert Einstein.
Commas with but
Use a comma before the coordinating conjunction but if it is joining two independent clauses:
If but is not joining two independent clauses, leave the comma out.
Commas with and
When correcting a comma splice by adding and—that is, when joining two independent clauses with and as a coordinating conjunction—put the comma before and.
When you have a list that contains only two items, don’t use a comma before the and.
Avoiding comma splices
When you want to join two independent clauses, you need a conjunction or a semicolon; a comma alone isn’t strong enough to join them. This kind of mistake is called a comma splice.
You can fix a comma splice by adding a conjunction or changing the comma to a semicolon.
Or you can simply write the two independent clauses as separate sentences.
Commas with relative clauses
A clause that is nonrestrictive offers extra information about something you have mentioned in a sentence, but that information isn’t essential for identifying the thing you’re talking about. Nonrestrictive clauses are usually introduced by which or who and should be set off by commas.
The clause “which Chester recommended” is nonrestrictive because “Posey’s Cafe” is already specific. Identifying it as the restaurant recommended by Chester doesn’t narrow it down any further.
The clause “whom I love dearly” is nonrestrictive because you could remove it and it would still be clear what person you’re talking—“my wife” is already specific.
A clause that is restrictive adds information that is necessary in order to identify whatever it is referring to. Restrictive clauses are often introduced by that or who and should never be set off by commas.
The clause “that Chester recommended” is essential information in the sentence above. If you removed it, there would be no way to tell which restaurant you were talking about.
Commas with appositives
An appositive is a noun or noun phrase that refers to the same thing as another noun in the same sentence. Often, the appositive provides additional information about the noun or helps to distinguish it in some way. If you could remove the appositive without changing the meaning of the sentence, it is said to be nonessential and should be set off with commas. If the appositive is necessary, it’s said to be essential and should not be set off with commas.
Nonessential appositives
My partner, Angela, is a wonderful cook.
The painter, one of the city’s most promising young artists, began showing his work in galleries before he was sixteen.
Chocolate, my favorite treat, always makes me feel better after a bad day.
Essential appositives
Edgar Allan Poe’s poem “The Raven” is a classic.
Nick Jonas’s brother Kevin is the most underrated Jonas. The detective Sherlock Holmes is one of literature’s greatest sleuths.
Commas with introductory phrases
A comma normally follows a participial phrase that introduces a sentence:
Grabbing her umbrella, Kate raced out of the house.
Confused by her sister’s sudden change in mood, Jill stayed quiet.
When an adverbial phrase begins a sentence, it’s often followed by a comma, but it doesn’t have to be, especially if it’s short. As a rule of thumb, if the phrase is longer than about four words, use a comma. You can also use a comma after a shorter phrase when you want to emphasize it or add a pause for literary effect.
After the show, Cleo will be signing autographs.
Behind the building there is enough space to park two limousines.
Without knowing why, I crossed the room and looked out the window.
In 1816 life was very different.
Suddenly, a frightened black cat sprang from the shadows.
But if there is a chance of misreading the sentence, use the comma:
Commas with dates
When writing a date in month-day-year format, set off the year with commas.
July 4, 1776, was an important day in American history.
I was born on Sunday, May 12, 1968.
If you are using the day-month-year format, however, commas are unnecessary.
Applications are due by 31 December 2024.
Use a comma between a day of the week and a date:
On Tuesday, April 13, at three o’clock, there will be a meeting for all staff.
Please join us on Saturday, June 10, 2023, for the marriage of Annie and Michael.
When you are referencing only a month and year, you don’t need a comma.
The region experienced record rainfall in March 1999.
Commas with coordinate adjectives
When multiple adjectives modify a noun to an equal degree, they are said to be coordinate and should be separated by commas. One way to tell whether the adjectives are coordinate is to try switching the order of them. If the sentence still sounds natural, the adjectives are coordinate.
That man is a pompous, self-righteous, annoying idiot.
That man is a self-righteous, annoying, pompous idiot.
The sweet, scintillating aroma of cinnamon buns filled the kitchen.
The scintillating, sweet aroma of cinnamon buns filled the kitchen.
If multiple adjectives are used but are not coordinate—that is, if one of them is more closely related to the noun being modified than the other(s), and thus they sound unnatural if the order is changed—don’t separate them with a comma.
Commas with interrupters or parenthetical elements
Interrupters are little thoughts that pop up in the middle of a sentence to show emotion, tone, or emphasis. A parenthetical element is a phrase that adds extra information to the sentence but could be removed without changing the meaning of the sentence. Both interrupters and parenthetical elements should be set off with commas.
Commas between direct quotes and attributive tags
An attributive tag is a phrase, like “they said” or “she claimed,” that identifies the speaker or writer of a quote or piece of dialogue. Attributive tags can come before, after, or even in the middle of a quote. Use commas to separate attributive tags from quotations.
The professor remarked, “How attentive you have been today!”
“Once you know the solution,” Tiffany said, “the whole problem seems very simple.”
“You have ice cream on your nose,” my friend giggled.
“When you leave the house,” my mother yelled, “don’t slam the door!”
If a quotation before an attributive tag ends in a question mark or exclamation point, however, there’s no need for a comma.
Commas with quotation marks
In American English, commas always go before closing quotation marks.
“Pass me that thesaurus,” said Matthew.
“If you knew what was good for you, you’d finish that essay right now,” my roommate said.
“We’re going down to the soup kitchen to help serve dinner,” her mother called.
In British English, however, unquoted punctuation typically follows the quotation marks. If you are writing for a British audience, put the comma after the closing quotation mark. (Furthermore, British English tends to use single quotes rather than double quotation marks.)
Commas with parentheses
Parentheses are used to give additional information to the reader—information that might disrupt the flow of the sentence if written as a nonrestrictive clause. Commas may be placed after the closing parenthesis but not before either the opening or the closing parenthesis. If the sentence would not require any commas without the parenthetical material, it should not have any commas with it.
Commas with question tags
A question tag is a word or short phrase that is added to the end of a statement to turn it into a question. Writers often use question tags to encourage readers to agree with them. A question tag should be preceded by a comma.
These willow trees are beautiful, aren’t they?
You didn’t actually write a 600-page vampire romance novel, did you?
I know, right?
Commas with direct address
When addressing another person by name, set off the name with commas.
Mom, I can’t find my shoes!
Cleo, there’s someone on the phone for you.
Hello, Chester.
Commas with as well as
You generally don’t need a comma before the connective phrase as well as. However, if you want the element of a sentence introduced by as well as to be read as an interrupter or a parenthetical, setting it off with a comma or pair of commas can communicate that.
Please proofread for grammatical mistakes as well as spelling.
Spelling mistakes, as well as grammatical errors, are distracting to readers.
Commas with such as
The phrase such as requires commas if it introduces a nonrestrictive clause.
Coniferous trees, such as pine and spruce, do not drop their needles in the winter.
If such as introduces a restrictive clause, omit the commas.
Trees such as pine and spruce do not drop their needles in the winter.
Commas with too
Using a comma before the adverb too is generally unnecessary but not incorrect.
I like bananas too.
I too like bananas.
Setting too off with commas can add emphasis or make the sentence easier to parse.
I like bananas, too.
I, too, like bananas.
Comma mistakes to avoid
There are a few places in a sentence where a comma should (almost) never appear.
Between subjects and verbs
With few exceptions, a comma should not separate a subject from its verb.
Writers are often tempted to insert a comma between a subject and verb this way because speakers sometimes pause at that point in a sentence. But in writing, the comma only makes the sentence seem stilted.
Be especially careful with long or complex subjects:
In compound subjects or objects
In general, don’t put a comma between two nouns that appear together as a compound subject or compound object.
Occasionally, when a subject or object is made up of two items and the second item is parenthetical, or both items are long, the second item can be set off between two commas.
She, and her cat, live there.
The irritating behavior of certain other members of the food coop, and the recent steep increase in prices of much of the produce there, inevitably dominated the conversation.
In these cases, the writer is using commas to let the reader know where in a sentence emphasis and pauses should fall. They are not grammatically necessary, so the compound subjects still take plural verbs.
In compound predicates
A compound predicate is what you have when the subject of a sentence is shared by more than one verb without being repeated. In a compound predicate that contains two verbs joined by a coordinating conjunction, a comma should rarely be used between the verbs
It’s easiest to make this mistake when the predicate is made up of long verb phrases.
However, it’s occasionally helpful to use a comma in a compound predicate to prevent misreading:
In the sentence above, you need the comma to make clear that it was Cleo who waved, not the man.
Between verbs and their objects
Don’t separate a transitive verb from its direct object with a comma.
With correlative conjunctions
Correlative conjunctions are conjunctions that come in pairs (such as either/or, neither/nor, and not only/but also) and connect words or phrases in a sentence to form a complete thought. Typically, commas are unnecessary with correlative conjunctions.
Between articles and nouns
Don’t use a comma between an article and a noun.
When speaking, we often pause while we think of the next word we want to say. In writing, though, there’s usually no reason to add this pause. If you’re writing dialogue and you specifically want to convey a pause while someone is thinking, use an ellipsis: I’ll have an . . . apple.
With than comparisons
Don’t use a comma before than when you’re making a comparison.
