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For their size, commas are deceptively tricky. Even experienced writers still get tripped up by the measly comma, that little squiggly punctuation mark that inserts a mid-sentence pause after listed items, before conjunctions, in compound and complex sentences, and in a variety of other grammatical situations. 

Even among those with a lot of writing experience, some comma questions still linger:

  • Do I need to put a comma before every conjunction?
  • Should I follow my introductory phrase with a comma? Do I need to?
  • I know lists generally use a comma, but what if my list only has two items?
  • If I insert a phrase, do I need a comma on both sides of it?

While our Punctuation Guide provides a comma overview in addition to a summary of other grammatical tools, this guide will focus on the comma in particular, giving a full breakdown of rules that will answer all your comma questions and concerns.

The Comma’s General Functions

In general, use a comma to separate the following from the main sentence:

  • Independent clauses: I’m in love with her, and I feel fine. (Credit to Paul McCartney.)
  • Introductory clauses or phrases: With a love like that, you know you should be glad. (Again, thanks Paul.)
  • Items in a list or series: I got beans, greens, potatoes, tomatoes. 
  • Nonessential clauses or phrases: Superwoman, the hero, saved her city.
  • Direct addresses: Larry, you need to stop parking your car in the middle of the street.
  • Quotations: Oprah Winfrey said, “You don’t become what you want. You become what you believe.”
  • Dates and numbers: I’m about $1,300 short on my mortgage this month.

Why Omitting Commas is a Fatal Flaw

Commas help us organize our sentences, so readers can keep track of our core clause and the various nonessential items or clauses that branch off of it. When a sentence contains an inappropriate use of a comma or is missing a comma, the reader might misinterpret critical information within the sentence or have to strain and struggle to understand the sentence’s basic idea. The more complicated the sentence, the more costly the comma omission becomes:

Correct comma: Before I go, I want to thank you for your hospitality, generosity, and the food you cooked, which I enjoyed a lot, by the way.
Missing commas: Before I go I want to thank you for your hospitality generosity and the food you cooked which I enjoyed a lot by the way.

Correct comma use: Costa Rica, a land luxuriant with green, shimmers with leaves, the ocean waves, and surprisingly, spider monkeys.
Missing commas: Costa Rica a land luxuriant with green shimmers with leaves the ocean waves and surprisingly spider monkeys.

Readers have to work much harder to comprehend the comma-less sentences above, and they might just give up altogether. Commas unlock the potential to craft complex, beautiful, specific, imaginative sentences like the green ones above, without sacrificing clarity. Use the below comma rules to unlock your sentence’s potential.

When to Use a Comma

#1: Use a comma to separate independent clauses.

The comma precedes a coordinating conjunction (for, and, nor, but, or, yet, so) to separate independent clauses within a sentence.

Incorrect: The rain sounds nice outside and it helps me fall asleep. 
(Insert a comma before and.)
Correct: We won most of our games this season, so we made the playoffs.

Incorrect: My brother is a skilled chess player, yet lacks confidence. 
(Omit the comma because it’s followed by a dependent, not independent clause.)
Correct: I just got a new pet turtle, but I still don’t feel satisfied.

#2: Use a comma to separate an introductory clause, introductory phrase, or any word that comes before the sentence’s main clause. 

A comma provides a pause between your core sentence (subject + predicate) and its introduction, whether that introduction is a clause, phrase, or single word:

Introductory clause:
Incorrect: Although I studied a lot last night I still feel nervous about this text. 
(Needs a comma after night.)
Correct: When we woke up on Christmas morning, we saw that someone had eaten the cookies.

Introductory phrase:
Incorrect: Upon waking my son always remembers his dreams. 
(Needs a comma after waking.)
Correct: After school, my friends plan to get boba downtown.

Introductory word: 
Incorrect: Honestly you need to go away. 
(Insert comma after honestly.)
Correct: Actually, you’ve been right this whole time.

#3: Use a pair of commas to separate nonessential clauses, phrases, or words.

Nonessential (or nonrestrictive) clauses or phrases do not play an essential part in the core sentence’s information. A clause or phrase is nonessential if, when you remove it, the sentence still makes sense. 

If the nonessential clause falls in the middle of the sentence, insert a comma before and after it, to denote pauses; if the clause begins or concludes the sentence, omit the former or latter comma, respectively. Keep in mind that nonessential clauses and phrases may begin with a relative pronoun (who, where, when, which, that) that refers to the noun preceding it.

Incorrect: Serena Williams a dominant tennis player won Wimbledon seven times. 
(Insert commas after Williams and player.)
Correct: Paulo Coelho’s The Alchemist, a novel that blurs the lines between self-help and fiction, tells the story of a young boy’s journey to listen to his heart.

Incorrect: I lost my phone in the ocean where my friend and I had gone swimming. 
(Insert comma after ocean because the following part is nonessential information.)
Correct: People always take photographs on the red carpet, where celebrities get to show off their outfits.

Incorrect: Atticus Finch riles up the town of Maycomb, when he decides to defend Tom Robinson in court. 
(Omit the comma because it precedes a clause essential to the sentence’s meaning.)
Correct: Harry Potter remains fearless when confronting Voldemort. 
(No comma necessary to precede the essential phrase starting with when.)

Reminder: Appositive phrases often (but not always) qualify as nonessential.

Appositive phrases, noun phrases or words that rename and/or modify nouns next to them, are usually nonessential, requiring commas. However, in some contexts, appositive phrases are essential, not requiring commas.

Essential appositive phrase: The wide receiver Jerry Rice leads the NFL in all-time touchdown receptions.
Nonessential appositive phrase: Jerry Rice, the wide receiver, leads the NFL in all-time touchdown receptions.

In the former example, the name Jerry Rice is critical in distinguishing which player holds the record, so the appositive phrase Jerry Rice is essential. In the latter example, the description the wide receiver is not critical to the record holder’s identity, so while it is a useful elaboration, it requires commas because it’s nonessential.

Appositive phrases often begin with possessive pronouns (my, his, her…) or articles (the, a/an).

Incorrect: The Road tells the story of a boy journeying with his father the person he depends on most. 
(Include a comma to precede the appositive phrase, which begins with the.)
Correct: In Toy Story, Buzz Lightyear arrives in Andy’s room, a place unfamiliar to Buzz.

#4: Use commas to separate three or more items in a series.

The term item refers to a single word, phrase, clause, name, or any other entity distinguished and listed within a series.

Incorrect: There are three things I know I can rely on: sunset sunrise and my grandma’s baking skills. 
(Insert commas after sunset and sunrise.)
Correct: My dog engages in three primary activities: going for a walk, taking a nap, and staring at me while I prepare food.

Incorrect: Our company should focus on targeting a specific audience prioritizing quality over quantity and utilizing new marketing tools. 
(Insert commas after audience and quantity.)
Correct: Mesopotamia, Egypt, Maya, and China are four of the world’s most ancient civilizations.

Separate two-item lists using the word and without any commas. 

Correct: My favorite sandwich is peanut butter and jelly.

#5: Use commas to separate two or more coordinate adjectives that describe the same noun.

Do not include a comma between the final adjective and the noun itself, and only use a comma if the adjectives are coordinate, or equal, meaning they hold equal importance in describing the noun. If the adjectives are not coordinate, omit the comma.

You can make sure you have coordinate adjectives by seeing if the description retains its meaning when you switch the adjectives. If the description’s meaning stays the same with the adjectives switched, they are coordinate (equal) adjectives. Additionally, if you can substitute the word and in place of the comma between the adjectives, and the description retains its meaning, they are coordinate adjectives.

Coordinate adjectives:

  • It was a dark, stormy night.
  • She gave me a sharp, somber gaze before closing the door.
  • The cold, thrashing ocean whipped the boat back and forth.

Non-coordinate adjectives

  • This is the last friendly warning you will receive. 
  • We just signed up for the discounted jazz lessons.
  • He has given me many generous gifts over the years.

Incorrect: John Green’s Looking for Alaska features a determined young protagonist on the search for a girl he loves.
(Insert a comma between coordinate adjectives, determined young.)
Correct: Chinua Achebe’s Things Fall Apart charts years in the life of the proud, stubborn Okonkwo.

Incorrect: In the morning, Atticus takes pensive sips from his full, coffee mug.
(Non-coordinate adjectives full and coffee should not have a comma between them.)
Correct: My mom feels concerned about the volatile real estate market.

#6: Use a comma to emphasize coordinate elements or a shift, toward the end of a sentence.

When a sentence contains contrasted or coordinate elements, which means elements that parallel, contrast, or relate in some way, inserting a pause (via comma) emphasizes the relationship between the two elements and helps the reader distinguish between them. These coordinated elements can be any part of speech (nouns, adjectives, verbs, etc.) and the emphasis comma applies whether the coordinated relationship is a contrast, comparison, or another form of coordination.

Additionally, use a comma to emphasize a sudden shift in tone or focus at the end of a sentence.

Incorrect: My mom told me that breakfast not dinner is her favorite meal of the day.
(Insert comma after breakfast and after dinner to emphasize the nouns’ coordination.)
Correct: At the end of To Kill a Mockingbird, Scout learns that growing up means developing integrity, not popularity.
Correct: I drove home feeling tired, yet alive.
Correct: We opened the oven to find our cake burnt, nearly decimated.
Correct: When you come to a fork in the road, always go left, never right.

#7: Use commas to separate descriptions at the middle or end of a sentence that refer back to the sentence’s beginning.

These lingering descriptions, separated from their subjects by at least a few words, are called free modifiers, which usually refer back to the sentence’s main subject or clause. Use a comma to set these descriptions apart from the words that immediately precede them, indicating the free modifier’s connection to the subject or clause that comes earlier in the sentence.

Keep in mind that when using a free modifier, it should be clear which subject the description modifies. If there’s any confusion about which subject is modified by the description, for example if the sentence has multiple applicable subjects, rearrange the sentence to place the description adjacent to the noun it modifies.

Incorrect: Elton John played the piano for hours a smile on his face.
(Insert a comma before a, to set off the free modifier.)
Correct: Educated’s narrator Tara Westover goes through quite a journey in her book, learning new things the whole way.

Incorrect: George scolded Lennie, an unhappy look on his face.
(Unclear which subject the free modifier describes.)
Correct: An unhappy look on his face, George scolded Lennie.
(In this case, placing the description near its subject (George) helps clarify.)

Incorrect: Sandra Cisneros uses The House on Mango Street to explore the topics of family and growing up overlapping the two through Esperanza’s experience. 
(Insert a comma before overlapping to set off the free modifier.)
Correct: Esperanza undergoes a variety of disillusioning experiences, gradually becoming skeptical of people in her life.

#8: Use a comma to separate all dates, geographical locations, and numbers over three digits long.

For dates, put commas around the year to separate it from the rest of the sentence.

Incorrect: Adele released her album 19 on January 28 2008 instantly selling many copies.
(Insert a comma before and after the year 2008.)
Correct: Taylor Swift’s Folklore, released on July 25, 2020, became the biggest album of that year.

For addresses, use a comma to separate each element of an address except the zip code.

Incorrect: Kingsboro Community College is located at 2001 Oriental Boulevard Brooklyn New York 11235.
(Insert a comma after each element in the address.)
Correct: The City College of New York is located at 160 Convent Avenue, New York, New York 10031.

For titles that follow someone’s name, place a comma after the name and before the title. Keep in mind that Jr. and numerals are not titles.

Incorrect: The article was written by Emma Sourakis PhD.
(Insert a comma before the post-name title)
Correct: According to Paul Madden, MD, zinc supplementation is especially beneficial in the winter.

For numbers longer than three digits, use commas to separate digits into groups of three, after every third digit from the final (rightmost) digit.

Incorrect: Kareem Abdul-Jabar is the NBA’s all-time leading scorer, with 38387 career points.
(Insert a comma to make the number 38,387.)
Correct: Throughout his career, Abdul-Jabar attempted 28,307 shots from the field.

For geographical locations with two or more place names (city, province, region, state, country, continent), use a comma after each place, including the finally named place, unless it concludes the sentence (in which case, use a period).

Incorrect: John Lennon was born in Liverpool United Kingdom.
(Insert a comma between the two place-names in the geographical location.)
Correct: The singer Adele was born in Tottenham, London, United Kingdom.

#9: Use commas to indicate a direct address.

When speaking directly to an audience, and referring to them by name, title, or direct reference, use commas on either side of the reference to set it apart from the rest of the sentence. This clarifies that the name’s role is distinct from the core sentence itself.

Incorrect: Ricky I’ve told you so many times to stop climbing on the table.
(Insert a comma after the direct address.)
Correct: You must know by now, Professor, that I understand the course material very well.

#10: Use commas to separate dialogue, speech, or a quotation from the main text.

When a new voice enters the sentence, whether that be a quotation from an outside source, or a character speaking, distinguish this quotation text from the main text by using commas (as well as quotation marks) on both sides: the preceding comma goes outside the quotation marks, and concluding comma goes inside the quotation marks. 

For more information on commas and quotation marks in this context, check out our Punctuation Guide.

Incorrect: Throughout Brave New World, John the Savage undergoes experiences that lead him to say “If one’s different, one’s bound to be lonely.”
(Insert a comma after say.)
Correct: When John the Savage says, “I want to know what passion is. I want to feel something strongly,” he shows how his culture has robbed him of the natural propensity to feel.

Incorrect: The monster in Mary Shelley’s Frankenstein utters the line “There is something at work in my soul, which I do not understand” expressing his innate curiosity.
(Insert a comma after line and after understand before the quotation mark.)
Correct: Highlighting the fine line between good and evil, the monster exclaims, “If I cannot inspire love, I will cause fear!”

#11: Use commas to insert a pause, when necessary, to pace your sentence or prevent confusion.

The comma’s most basic and general function is to prevent confusion, which it achieves by inserting a pause that paces the sentence. Whenever a sentence’s language risks confusion, muddling, or excessive complexity, seek out opportunities to insert commas, separating ideas and clauses into sections so that readers can understand the text as easily as possible.

Incorrect: When you a writer told me that I should use more specific words I knew I should listen.
(Insert commas to set off all phrases and clauses that separate from the sentence’s main clause.)
Correct: When you, a writer, told me that I should use more specific words, I knew I should listen.

Incorrect: Every year my family travels to Pine Mountain Lake our favorite vacation destination where we swim eat and generally relax.
(Insert commas to set off all phrases and clauses that separate from the sentence’s main clause.)
Correct: Every year, my family travels to Pine Mountain Lake, our favorite vacation destination, where we swim, eat, and generally relax.

Incorrect: I always overeat a big mistake.
(Insert a comma after overeat.)
Correct: I always overeat, a big mistake.

When Not to Use a Comma

Just as omitting a necessary comma can cause confusion, inserting an unnecessary or poorly placed comma can also cause confusion. Check out the situations below to make sure you use commas when you need them, and avoid them when you don’t.

 #1: Don’t use a comma to separate a subject from its verb.

Since a subject and a verb form a clause, do not use a comma to separate them; doing so would result in confusion for the audience, because commas usually separate distinct clauses from each other. Keep your clauses coherent and do not split subject-verb pairs with a comma.

Incorrect: The mustached man, bears a heavy burden.
(Omit the comma separating a subject and its verb.)
Correct: The mustached man bears a heavy burden.

Incorrect: My puppy, trotted along the sidewalk.
(Omit the comma separating a subject and its verb.)
Correct: My puppy trotted along the sidewalk.

#2: Don’t use a comma within a compound predicate.

A compound predicate is when a subject has multiple verbs. In this case, both verbs count as part of the same clause, so they should not be separated with a comma.

Incorrect: My husband made coffee, and went to work.
(Compound predicate should not have a comma between the verb phrases.)
Correct: The chefs worked together and created a delicious meal.

Incorrect: I saw the opportunity, and pounced.
(Compound predicate does not require a comma between the verbs.)
Correct: The cheetah saw its prey and pounced.

Wrapping up

For such a tiny amount of ink, the comma sure knows how to throw writers for a loop. But this tool should inspire excitement rather than fear, because when a writer masters the comma, they unlock a world of complexity, clarity, and detail that will take their writing to new levels. Commas are an integral part of good writing, and luckily, the more you use them, the more intuitive the comma’s rules become. So keep reading, keep trying to craft more complex and unique sentences, and don’t stop improving as a writer. Write on.

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Knowing the rules of comma use can help writers express their ideas clearly, avoiding confusion for readers.
Knowing the rules of comma use can help writers express their ideas clearly, avoiding confusion for readers.