When to Use Commas | 11 Comma Rules With Examples

More people struggle with commas than any other type of punctuation, and it’s usually because of a common misconception: “Use a comma wherever you pause.” Correct comma usage doesn’t come from vague hunches or intuition. It comes from knowing the specific rules about when to use commas and when to leave them out.

This guide covers the 11 comma rules that are most essential to clear writing with examples of each rule and tips to help you avoid errors. Scan the chart below for a quick overview, and explore each rule in more detail in the sections that follow.

Quillbot’s  Grammar Checker can show you where to use commas in any piece of writing.

Comma rules and examples at a glance

Comma rule 1: Compound sentences

Use a comma and a coordinating conjunction to join two complete sentences (aka independent clauses) in a compound sentence. The chart below shows how to use a comma before each of the seven coordinating conjunctions (“for,” “and,” “nor,” “but,” “or,” “yet,” “so”). Notice how each independent clause (underlined in blue) can stand alone as a complete sentence.

Commas in compound sentences 

Comma rule 2: Lists of three or more (the Oxford comma)

Use commas to separate items in a list, including a comma before the coordinating conjunction (e.g., “and”) that joins the last item to the list. A list can consist of three or more individual words or three or more groups of words that aren’t complete sentences. The chart below shows how to use commas in some of the most common types of lists, ranging from simple to elaborate.

Commas in lists of three or more

The comma that goes before the coordinating conjunction (usually “and” or “or”) is called a “serial comma” or an Oxford comma. While some publications and workplaces omit the Oxford comma, it’s usually required in academic writing, and it often prevents confusion. For example, the sentence below has two possible meanings when there’s no Oxford comma:

• The artist’s biggest influences were her parents, Frida Kahlo and Diego Rivera. [Are Frida and Diego the artist’s parents or two of three influences?]
• The artist’s biggest influences were her parents, Frida Kahlo, and Diego Rivera.

Comma rule 3: Introductory words, phrases, or clauses

Use a comma to show where introductory information ends and the main part of a sentence begins. Introductory information can be a transition word like “however,” a phrase like “after spring break,” or a dependent clause like “if you win the lottery.” Scan the chart below for examples of all three.

Commas after introductory elements

Comma rule 4: Nonessential information

When a sentence has nonessential information right after a noun that it describes, use commas to separate it from the rest of the sentence. For example, you can follow a noun in a sentence with another noun, phrase, or clause that gives extra (but not essential) information. You can tell that information is nonessential when the sentence has the same meaning without it. Nonessential information usually goes in the middle or at the end of a sentence.

There are two main types of nonessential information: nonrestrictive appositives and nonrestrictive clauses. Scan the chart below for definitions and examples of each type.

Commas an nonessential information 

Comma rule 5: Coordinate adjectives

Use commas to separate coordinate adjectives, which are two or more consecutive adjectives that independently modify the same noun. The trick to this comma rule is knowing the difference between coordinate adjectives and cumulative adjectives. In both cases, there are multiple adjectives modifying the same noun, but cumulative adjectives should not have commas. The chart below shows how to tell the difference.

Coordinate vs cumulative adjectives 

Comma rule 6: Signal phrases and quotations

Use a comma after a signal phrase that introduces a direct quotation. A signal phrase identifies who is speaking or writing and prepares the reader for the quotation that follows. It usually includes the speaker’s name and a reporting verb like “said,” “writes”/”wrote,” or “explains”/“explained.” Another type of signal phrase is “according to [speaker].”

Comma rule 7: Question tags

Use a comma before a question tag, which is a short question added to the end of a statement. A question tag includes an auxiliary verb (e.g., “is,” “are,” “can,” “does,” or “have”) and a pronoun that refers to the same noun as the sentence’s subject.

Comma rule 8: Direct address

Use commas to separate a person’s name when you’re writing directly to them. The term for this is “direct address,” and it’s most common in workplace correspondence, such as emails and Slack messages.

Comma rule 9: Dates

When a sentence includes a date in month-day-year format, use commas after the day and the year (when the sentence continues). You don’t need commas when writing dates in day-month-year format or when you’re only using the month and year.

Comma rule 10: Geographical locations

Use a comma to separate a city from a state, province, or country. If the sentence continues after the location, place another comma after the state or country.

Comma rule 11: Numbers greater than 1,000

When writing numbers that are 1,000 or greater, use commas to separate groups of three digits. Exceptions are years, page numbers, and street addresses.

Frequently asked questions about when to use commas

Do you put a comma before and?

You need a comma before “and” in two situations: compound sentences and lists of three or more.

• Compound sentence: Use a comma before “and” when it joins two complete sentences into one compound sentence.
  • Tessa baked an angel food cake, and Zoe made a charcuterie board.
• List of three or more (Oxford comma): Use a comma  before “and” when it’s before the last item in a list of three or more (unless you’re writing for a publication or workplace that doesn’t use Oxford commas).
  • The museum is open until 9:00 p.m. on Thursday, Friday, and Saturday.

You don’t need a comma before “and” when it’s between two words or phrases. These comma rules apply to all of the coordinating conjunctions (“for,” “and,” “nor,” “but,” “or,” “yet,” “so”).

Looking for more examples of when to use a comma before “and”? Ask Quillbot’s AI Chat.

What are the comma rules for dates?

There are two comma rules for dates that are written in month-day-year format:

• Always place a comma between the day and year (e.g., May  21, 2026).
• If you’re using a full date in the middle of a sentence, use a comma after the date and a comma after the year (Dolly was born on January 19, 1946, in Locust Ridge, Tennessee).

When you’re unsure about when to use commas in dates, ask Quillbot’s Grammar Checker to proofread your writing.

Does “not only but also” require a comma?

Like all correlative conjunctions, “not only … but also” does not typically require a comma (e.g., “The weather forecast calls for not only rain but also hail”).

The one exception to this is when it is used to join two independent clauses, which each have a subject and a verb (e.g., “Ava not only speaks Spanish, but she also is learning French”). This sentence could also be rephrased to not require a comma (e.g., “Ava not only speaks Spanish but also is learning French”).

A Quillbot grammar check can help ensure you’re using correlative conjunctions and commas correctly.

Do compound predicates need commas?

A compound predicate with only two verbs does not use a comma (e.g., “I made my bed and took a shower”).

For a compound predicate with more than two verbs, a comma is used to separate the verbs or verb phrases, and the coordinating conjunction (e.g., “and”) is placed before the last verb.

• If you use the Oxford comma (or serial comma), you place a comma before the conjunction (e.g., “I cooked, cleaned, and did laundry all day”).
• If you do not use the Oxford comma, you do not place a comma before the conjunction (e.g., “I cooked, cleaned and did laundry all day”).