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8 Comma Rules: When to Use a Comma (With Examples)
Commas are the most common punctuation mark in English and the most often misused. The good news is that a short list covers almost every situation. These 8 comma rules tell you when to use a comma, with correct and incorrect examples for each. The guide also covers when not to use a comma and how to fix a comma splice.
Quick answer: the 8 comma rules
Use a comma:
- Before "and," "but," or "so" joining two complete sentences
- After an introductory element
- Between items in a series
- Around nonessential information
- Between coordinate adjectives
- Around a name in direct address
- In dates, addresses, and large numbers
- To introduce or interrupt a quotation
Don't use a comma:
between a subject and its verb, between a verb and its object, before a restrictive clause, or to join two complete sentences on its own.
| Rule | Use a comma when... | Example |
|---|---|---|
| 1. Compound sentences | A coordinating conjunction joins two independent clauses | She finished the report, and her colleague submitted it. |
| 2. Introductory elements | A word, phrase, or clause comes before the main clause | After reviewing the data, the team revised its conclusions. |
| 3. Items in a series | You list three or more items | The report covered sales, marketing, and operations. |
| 4. Nonessential information | A clause or phrase adds detail the sentence doesn't need | My editor, who has a PhD in linguistics, reviewed the draft. |
| 5. Coordinate adjectives | Two adjectives describe the same noun independently | She gave a clear, concise presentation. |
| 6. Direct address | You speak to someone by name or title | Thank you, Dr. Carter, for your feedback. |
| 7. Dates, addresses, numbers | You write a full date, a city and state, or a number of 1,000 or more | The study was published on March 15, 2023, in Chicago, Illinois. |
| 8. Direct quotations | You introduce or interrupt a quotation | She said, "Turn right at the door." |
What Are the 8 Comma Rules?
The 8 comma rules below cover most of the commas you'll ever need. Each one names the situation, explains why the comma belongs, and shows a correct and an incorrect example.
1. Use a comma before a conjunction that joins two independent clauses
An independent clause is a group of words that could stand alone as a sentence. When two of them are joined by a coordinating conjunction, put a comma before the conjunction. The seven coordinating conjunctions are for, and, nor, but, or, yet, and so (remembered as FANBOYS).
- Correct: "He wanted to apply for the job, but the deadline had passed."
- Incorrect: "He wanted to apply for the job but the deadline had passed."
If the second part can't stand alone, skip the comma. "She finished the report and submitted it" needs no comma, because "submitted it" has no subject of its own.
2. Use a comma after an introductory element
When a sentence opens with a word, phrase, or clause before the main subject and verb, put a comma after that opening element. The comma tells the reader where the main sentence begins.
- Correct: "Before submitting the application, she proofread it three times."
- Correct: "However, the results were not significant."
- Incorrect: "Before submitting the application she proofread it three times."
Some style guides let you drop the comma after a very short introductory phrase, such as "In 2020 we moved." Keeping it is never wrong and is often clearer.
3. Use commas to separate items in a series
When you list three or more items, put a comma after each item except the last. The comma before the final "and" or "or" is called the Oxford comma or serial comma.
- With the Oxford comma: "The report covered sales, marketing, and operations."
- Without it: "The report covered sales, marketing and operations."
APA, MLA, and Chicago use the Oxford comma. AP style, used in journalism, leaves it out of simple lists. Whichever you choose, use it consistently. For examples, the style-guide breakdown, and the famous lawsuit, see our guide to the Oxford comma.
4. Use commas to set off nonessential information
Nonessential (or nonrestrictive) information adds detail that the sentence doesn't need to identify who or what you mean. Set it off with a comma on each side. Essential (restrictive) information gets no commas.
- Nonessential, with commas: "My editor, who has a PhD in linguistics, reviewed the manuscript."
- Essential, no commas: "The editor who reviewed the manuscript has a PhD in linguistics."
In American English, "which" usually introduces nonessential clauses (with commas) and "that" introduces essential ones (without commas). For the full test, see our guide to which vs. that.
5. Use a comma between coordinate adjectives
Coordinate adjectives each describe the noun on their own. Separate them with a comma. To test, put "and" between them or swap their order. If the sentence still sounds natural, use the comma.
- Coordinate, with a comma: "It was a long, difficult editing process." ("Long and difficult" works.)
- Cumulative, no comma: "She wore a bright red jacket." ("Bright and red" doesn't work, because "bright" describes the red.)
6. Use commas to set off direct address
When you speak to someone by name or title, set the name off with commas. Use one comma if the name starts or ends the sentence and two if it falls in the middle.
- "Thank you, Dr. Carter, for your feedback."
- "James, please review this section before we submit."
- "Let's eat, Grandma." (Without the comma, the sentence means something very different.)
7. Use commas in dates, addresses, and large numbers
Commas follow set conventions in these three places. When a full date or a city and state appear mid-sentence, a comma also follows the year or the state.
- Dates: "The study was published on March 15, 2023, in a peer-reviewed journal."
- Addresses: "The conference was held in Pittsburgh, Pennsylvania, in October."
- Numbers: Separate groups of three digits: 1,000; 25,000; 1,250,000.
No comma is needed with a month and year alone ("March 2023") or with a day-month-year date ("15 March 2023").
8. Use a comma to introduce or interrupt a direct quotation
Put a comma between a speaking verb, such as "said" or "asked," and the quotation. If the quotation is interrupted, use a comma on each side of the interruption.
- Introducing a quotation: She said, "Walk through the door and turn right."
- Interrupting a quotation: "The data," he explained, "doesn't support that conclusion."
In American English, commas and periods go inside the closing quotation mark. British English often places them outside unless they belong to the quoted words.
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See Proofreading ServicesWhen Else Do You Use a Comma?
Two more uses come up often enough to know, even though they fall outside the classic eight.
- Parenthetical and transitional expressions. Words like "however," "for example," and "in fact" take a comma on each side in the middle of a sentence: "The study, however, did not control for age."
- Contrasting elements. Set off a contrast introduced by "not": "It was the method, not the findings, that reviewers questioned."
When Should You Not Use a Comma?
Extra commas cause as many errors as missing ones. Leave the comma out in these situations.
| Don't put a comma... | Incorrect | Correct |
|---|---|---|
| Between a subject and its verb | The study published last year in the journal, found no effect. | The study published last year in the journal found no effect. |
| Between a verb and its object | She decided, to revise the draft. | She decided to revise the draft. |
| Before an essential clause | The article, that I cited, was published in 2021. | The article that I cited was published in 2021. |
| Right after a conjunction | She reviewed the draft and, sent her comments. | She reviewed the draft and sent her comments. |
| Between cumulative adjectives | She wore a bright, red jacket. | She wore a bright red jacket. |
| Between two verbs that share one subject | He opened the file, and printed it. | He opened the file and printed it. |
| To join two complete sentences on its own | The results were promising, the team proceeded. | The results were promising, so the team proceeded. |
What Is a Comma Splice and How Do You Fix It?
A comma splice joins two independent clauses with only a comma. It's one of the most common errors editors flag. There are three easy fixes.
- Comma splice: "I finished the article, I printed it."
- Add a conjunction: "I finished the article, and I printed it."
- Use a semicolon: "I finished the article; I printed it."
- Make two sentences: "I finished the article. I printed it."
A semicolon works only when both halves are complete sentences. For when to choose a semicolon or a colon, see our guide to colon vs. semicolon.
Comma Tips for Writers Whose First Language Isn't English
Comma conventions differ from language to language, so English rules can feel arbitrary at first. These four points cause the most trouble.
- No comma before "that" when it introduces an essential clause, even though some languages use one there.
- A comma after an opening transition, such as "However," "Therefore," or "In addition."
- No comma between a verb and its object, even when the object is long.
- No comma alone between two complete sentences. Add a conjunction or use a period.
Catch the commas you can't see in your own draft
At Editor World, you choose your own native English editor, and no AI is used at any stage.
Choose Your EditorFrequently Asked Questions
What are the 8 comma rules?
Use a comma (1) before a conjunction joining two complete sentences, (2) after an introductory element, (3) in a series, and (4) around nonessential information. Also use one (5) between coordinate adjectives and (6) around a name in direct address. The last two are (7) dates, addresses, and large numbers and (8) introducing or interrupting a quotation.
How do you know when to use a comma?
Ask what the comma is doing. It should separate list items, mark the end of an introductory element, set off extra information, or join two complete sentences together with a conjunction. If a comma would split a subject from its verb or a verb from its object, leave it out. Reading the sentence aloud helps, but a pause alone isn't a reliable test.
Do you put a comma before "and"?
Sometimes. Use one when "and" joins two complete sentences, as in "She wrote the report, and he edited it." Many writers also use one before the final "and" in a list of three or more, which is the Oxford comma. Don't use one when "and" joins two words, two phrases, or two verbs that share a subject.
Do you put a comma after "however"?
Yes, when "however" starts a sentence and means "on the other hand": "However, the results differed." In the middle of a sentence, it takes a comma on each side. Between two complete sentences, use a semicolon before it: "The data was strong; however, the sample was small."
What is a comma splice?
A comma splice joins two complete sentences with only a comma, as in "I finished the article, I printed it." Fix it by adding a conjunction after the comma, replacing the comma with a semicolon, or splitting it into two sentences. It's one of the most common punctuation errors in student and professional writing.
When should you not use a comma?
Don't put a comma between a subject and its verb, between a verb and its object, or before an essential clause. Also leave it out right after a conjunction, between cumulative adjectives like "bright red," and between two verbs that share one subject. And never use a comma by itself to join two complete sentences.
Do commas go inside quotation marks?
In American English, yes. Commas and periods always go inside the closing quotation mark: "The data," he said, "is clear." British English often places them outside unless they belong to the quoted words. Question marks and exclamation points go inside only when they're part of the quotation.
Is there a space after a comma?
Yes. Put one space after a comma and no space before it. The exception is large numbers, where commas separate groups of digits with no spaces, as in 1,250,000. In some languages the spacing rules differ, so check this when writing in English after another language.
Should I use the Oxford comma?
Use it if your style guide requires it. APA, MLA, Chicago, and AMA all do. AP style, common in journalism, leaves it out of simple lists. If no guide applies, using it consistently is the safer choice, because it prevents more misreadings than it causes.
Can an editor fix comma errors in my writing?
Yes. A proofreader checks every comma against the rules and your style guide. That includes the splices and missing introductory commas that are hard to see in your own draft. At Editor World, you choose a native English editor, and most editors offer a free sample edit of your first 300 words.
Related Guides
For every punctuation mark in one place, see our guide to the 14 punctuation marks in English. For the errors that show up most in theses and journal articles, read common punctuation errors in academic writing. For the other marks that trip writers up, see apostrophes and hyphens.