Rules to Use a Comma

The comma is a punctuation mark that indicates a pause between the words of a sentence .

• Anita, Rita, and Nesbit are kicking a ball.
• Maya wrote a book, which Anita then edited for her.
• Nesbit, a complete geek, loves nothing better than to tinker with technology.
• This parcel was shipped from Esperance, Australia, on May 21, 1971.
• Rita always says, “To fly is to live.”
• This may be important, but it isn’t urgent, is it?

Unfortunately, commas are easily misused. In this article, we discuss how to use the comma correctly—when to use it and when not to.

In lists and series

Use commas to separate the elements in a list or series.

• Maya likes books, travel, and tea.
• We visited three countries: Ukraine, Serbia, and Armenia.
• Lulu painted the chairs blue, green, yellow, and red.
• Tumkin had milk, muesli, and fruit for breakfast.

The serial comma in a list is optional.

The serial comma

The serial or Oxford comma is placed after the second-last element in a series and is the comma before the conjunction (and, or, but, etc.). Using this comma can help avoid confusion.

Confusing: My inspirations are my parents, Nelson Mandela and Mother Teresa.

The serial comma after Nelson Mandela clarifies that this list has three distinct items: (1) parents, (2) Nelson Mandela, and (3) Mother Teresa.

Many major style manuals, such as the Chicago Manual of Style and the APA Publication Manual, recommend using the serial comma, while others, like the AP Stylebook, don’t.

The serial comma is common in American usage. In British style , it is generally used only when required to clarify meaning.

Comma before etc.

If a list ends in etc. , precede the abbreviation with a comma (since etc. represents all the remaining items in such a list).

• The box contained books, CDs , files, etc.
• Buntings, wrappers, etc. were strewn across the floor.

Some writers insert a comma both before and after etc. when it appears mid sentence.

The table was loaded with all manner of confectionary: cakes, cookies, candies, etc., jostled with jams and jellies.

This second comma, though, is going out of fashion. For instance, the Chicago Manual of Style no longer recommends it.

Between independent clauses

A comma is often used between two independent clauses joined by a coordinating conjunction like and, but, or, yet, and so. (An independent clause is one that can stand by itself as a sentence.) The comma separates the two clauses from each other for the reader.

• The cat sat on the mat, and the dog lay on the rug.
• You can call me to check, or I can just email you when it’s done.
• Maya bought a new umbrella for the trip, but it never rained.

The comma between independent clauses is not a grammatical requirement, although many (including the Chicago Manual of Style and APA Publication Manual) recommend its use. It appears more frequently in American than in British English. In creative writing, you may omit the comma to control sentence flow. In business and academic writing however, commas between independent clauses can make longer sentences easier to read.

The comma is often omitted when the two clauses are short.

• She sang and he danced.
• I can and I will.

A comma is not usually required in a compound predicate , where the conjunction simply joins two parts of the same clause.

• The cat sat on the mat and coughed up a hairball.
• You can call me or wait for an email.
• Farley bought a new umbrella but forgot to take it to Fiji.

Insert a comma if not using one would cause confusion.

Confusing: Lulu took one look at the man who had walked into the room and fainted.

After a subordinate clause

When a subordinate (or dependent) clause is used to start a sentence, a comma after the clause indicates a slight pause and improves readability.

• If it starts raining frogs, find shelter.
• When Poco gets angry, his eyeballs explode.
• Because you love him, you must leave him.
• Until Rita stands on Everest’s summit, she won’t stop trying.

The comma is generally omitted if the independent clause comes first.

• Find shelter if it starts raining frogs.
• Poco’s eyeballs explode when he gets angry.
• You must leave him because you love him.
• Rita won’t stop trying until she stands on Everest’s summit.

Before a contrast clause

Insert a comma before contrast clauses . These clauses imply contrast and begin with words like although, though, whereas, while, and even if. (The slight pause lent by the comma emphasizes the contrast.)

• She speaks our language, although she is Martian.
• Maya likes tea, while Tumkin prefers coffee.

Of course, when while means “at the same time as” rather than “whereas,” no contrast is implied, and the comma should be omitted.

• Nothing had changed while she was away.

Around nonessential elements

Enclose within commas a phrase or clause that is nonessential (or nonrestrictive). A nonessential element provides extra information and can be removed from a sentence without affecting its meaning.

• Farley, who is shockingly unfortunate, fell down the stairs.
• This museum, founded in 1903, is home to many priceless artifacts.

If information is essential to the meaning of a sentence, don’t put commas around it.

The man who stole my purse has been caught.

The relative clause “who stole my purse” is essential to the meaning of this sentence. If someone said, “The man has been caught,” you’d ask, “Which man?”

The perpetrator has already been named: Farley. Thus, the clause “who stole not only my purse . . .” provides additional details and is nonessential.

Around nonessential appositives

Enclose nonessential appositives in commas. (An appositive is a phrase that refers to the same person or thing as another phrase.)

• George Washington, the first president of the United States, was a Freemason.
• My mother, Anita, has published a book of poems.
• Rita’s lifelong ambition, to ride a motorbike down a mountainside, has been fulfilled.
• Beside the stairs was a hat, a hat with a head still in it.
• Rita is a gambler, a woman who likes to take chances.

Don’t enclose essential appositives in commas. Such appositives provide information necessary to identify the person or thing being spoken about.

Nesbit’s friend Tumkin is smart and funny.

After an introductory phrase

To improve readability, insert a comma after the introductory phrase in a sentence, especially a phrase four words or longer.

• In the afternoon, Maya drank a cup of tea.
• To bake a cake that is moist and fluffy, you must preheat your oven to the right temperature.

The comma is often omitted if the introductory phrase is short.

• Last year we sold our house.
• To write you must read.

Use a comma after an introductory phrase that might otherwise be confusing.

Confusing: Sadly Farley chopped off his finger.

After a sentence adverb

A comma is often placed after a sentence adverb (e.g., clearly, fortunately, obviously) to indicate that this adverb modifies the entire sentence.

• Clearly, it’s my fault.
• Fortunately, Nesbit can get us out of this maze.
• Obviously, Poco is lying through his teeth.
• Sometimes, Lulu likes to dance by moonlight.
• Together, they walked into the tunnel.

With conjunctive adverbs

A conjunctive adverb (e.g., however, therefore), used between two clauses or sentences, is often followed by a comma.

• I would have called you; however, I didn’t want to wake you up.
• A comma indicates a pause. Therefore, overusing this punctuation mark can affect sentence flow and make writing difficult to read.
• We had locked every door and window; nevertheless, we lay awake the entire night.
• Moreover, our data shows that people are happier than ever before.

To mark an interruption

An adverb or phrase that interrupts sentence flow is enclosed in commas.

• And then, unbelievably, he started to sing.
• Poco, as you know, is a narcissist.
• He is, despite it all, still a friend.
• I am, however, most disappointed by the result.

To set off exclamations or interjections

Set off interjections or exclamations from surrounding text by using commas.

• Yes, of course, I’ll send you the specifications.
• No, I don’t know where Farley is.
• Wow, that’s a brilliant idea.
• And then, my goodness, she swallowed the sword.
• Gosh, is that really the time?
• Oh, I’m fine as can be.

If you want an interjection to stand out even more, you can use em dashes (or spaced en dashes).

• And then—my goodness—she swallowed the sword.

To enclose direct speech

When you quote someone’s words exactly, using quotation marks, enclose the speech in commas.

• Tumkin said, “I’ll call you from Fiji.”
• Anita said, “This algorithm will never work,” and sniffed.
• “I think I’ve broken my arm,” cried Farley.
• Rita stopped chewing to say, “There’s an earthworm in my spaghetti,” and went back to enjoying her pasta.

Don’t use commas in reported speech—that is, if you are not quoting someone verbatim.

• Incorrect: Tumkin said, he would call me from Fiji.
  Correct: Tumkin said he would call me from Fiji.
• Incorrect: Anita said that, the algorithm would never work.
  Correct: Anita said that the algorithm would never work.

Between coordinate adjectives

Use commas between multiple adjectives modifying the same noun if they are coordinate (i.e., if they would sound fine when joined using and).

• We found some musty, moth-eaten woolen socks at the back of the drawer.
• Lulu is truly a kind, caring, and faithful friend.
• This is a beautiful, spacious room.

Commas are not generally used when the adjectives are cumulative rather than coordinate—that is, when the adjectives build up on each other to modify the noun, and their order is not reversible.

Unnecessary: He was a kind, old man.

The order of the two adjectives is not reversible. “He was an old kind man” would sound wrong. Therefore, the comma here is unnecessary.

The simplest way to check whether adjectives are coordinate and require commas is to try using the word and between them. If using and sounds natural, feel free to insert commas instead.

Sounds fine: Tumkin is a smart and intelligent man.

Before a question tag

Insert a comma before an interrogative fragment that forms a question tag .

• Rita’s gone home, hasn’t she?
• Poco’s yelling again, isn’t he?
• It isn’t still raining, is it?

To indicate contrast

When two parts of a sentence stand in contrast to each other, using a comma makes the contrast clearer.

This book is mine, not yours. I’ll go to Mars, but only if you come with me. I ate the entire sandwich, even though I hate pickles.

In direct address

Use the vocative comma to address someone. Enclose the person’s name or form of address in commas.

• Hello, Lulu, how are you?
• Sorry, Mr. Remy, your flight has been canceled.
• Congratulations, ma’am!
• Rita, did the cab company call?
• Happy holidays, everyone!

The vocative comma is going out of fashion. For example, most people will write “Hi John” rather than “Hi, John” in an email salutation. In carefully edited prose though, a vocative comma is still preferred. Also, use the vocative comma when not using one would cause confusion: compare “I’m cooking, my love” with “I’m cooking my love.”

In dates

In American usage, commas set off the year in an exact date.

• Maya was born on July 18, 1981.
• It was on September 23, 1999, that a spaceship landed on a glacier in Greenland.
• On December 22, 1999, Farley was abducted by aliens.

Don’t use commas when you mention only the month and year.

• Poor: We visited Greenland in July, 1997.
• Preferred: We visited Greenland in July 1997.

In British English, commas are often omitted because the day comes before the month, and typographical separation is not necessary between day and year.

• The war ended on 18 June 1815.
• Farley went missing on 22 December 1999 and reappeared on 21 June 2019, not having aged a single day.

In addresses

Use commas to typographically separate the parts of an address.

• They lived in Kuta, Bali, in a little house at the edge of town.
• Please deliver the package to 30 Rockefeller Plaza, New York, NY 10112.
• Maya lived in Chiang Mai, Thailand, from 2020 to 2021.

Such commas come in pairs. When you set off parts of dates or addresses, remember to close the commas.

Incorrect: Our trip to Colombo, Sri Lanka got canceled

When laying an address out vertically, omit commas at the end of lines.

• 30 Rockefeller Plaza
  New York
  NY 10112
• Mars Visa Application Center
  Crater Park Building, Room 307, 3rd Floor
  11 East Street, Mallaby
  Westington