7 Comma Rules in English Grammar (With Examples for Clarity)

A comma may look small, but it carries a big responsibility in English writing. It separates ideas, adds pauses, and helps sentences flow in a way that readers can easily follow. When used correctly, commas bring clarity and rhythm; when misplaced or missing, they can change meaning entirely.

Consider this example:
✔ Let’s bake, Olivia.
❌ Let’s bake Olivia.

The first sounds like an invitation to cook together, while the second completely changes the meaning. That’s the difference a single comma can make.

What Is a Comma?

A comma (,) is a punctuation mark used to separate parts of a sentence and make its meaning clearer. It often represents a small pause in thought—shorter than a period but stronger than a space. Commas organize ideas, signal transitions, and guide readers through complex sentences without confusion.

In English grammar, commas can:

• Divide items in a list
• Separate clauses and phrases
• Set off extra or nonessential information
• Indicate direct address, tag questions, or introductory words

Example: After reviewing the data, the manager approved the plan, and the team celebrated the success.

Here, commas help the reader move smoothly from one idea to the next. Without them, the sentence would feel rushed and harder to follow. In short, commas bring order and balance to writing—they show where thoughts connect, pause, or shift naturally.

Below are the common comma rules in English grammar that you should know.

Rule 1: Use Commas in a Series or List

One of the most common uses of a comma is to separate three or more items in a series. This keeps your list organized and prevents ideas from blending together.

Example: We packed sandwiches, fruit, juice, and cookies for the trip.

Each comma divides the list clearly so the reader can process each item.

The final comma before and or or in a list is called the Oxford comma (or serial comma). It’s optional but often recommended because it prevents ambiguity.

Example:

❌ I dedicate this project to my parents, Sarah and Thomas.
✔ I dedicate this project to my parents, Sarah, and Thomas.

In the first sentence, it’s clear that Sarah and Thomas are separate from “my parents.” The second suggests Sarah and Thomas are the parents.

Rule 2: Use a Comma After Introductory Words or Phrases

A comma is often used after an introductory word, phrase, or clause to separate it from the main part of the sentence. This short pause helps readers recognize where the introduction ends and the main idea begins, keeping the sentence clear and easy to follow.

Introductory words like however, yes, no, well, finally, or indeed often appear at the start of sentences. Adding a comma after them prevents the sentence from feeling rushed. For example:

• Yes, I’ll join you for lunch.
• However, we’ll need to confirm the booking first.
• Well, that wasn’t what I expected.

The same rule applies to longer introductory phrases—groups of words that set up time, place, or condition before the main action. For example:

• After reviewing the data, the team adjusted their plan.
• In the middle of the night, the phone started ringing.
• To save time, we combined the two reports.

Sometimes, if the introductory phrase is very short and the meaning is clear, the comma can be omitted. For instance, In 2025 we’ll expand the project is perfectly fine without one, though In 2025, we’ll expand the project adds a slight pause for clarity.

Rule 3: Use a Comma Before a Coordinating Conjunction (FANBOYS)

A comma is placed before a coordinating conjunction when it connects two independent clauses—that is, two complete sentences that could stand on their own. This short pause before the conjunction helps readers process one idea before moving to the next.

The seven coordinating conjunctions are remembered by the acronym FANBOYS: for, and, nor, but, or, yet, so. When these words join two full sentences, a comma belongs before them. For example:

• The train was delayed, but everyone remained calm.
• I wanted to go out, yet the weather looked uncertain.
• She submitted her report, and the manager approved it immediately.

If the conjunction connects only two short phrases or single words, no comma is needed because the sentence doesn’t pause naturally. For example, He searched the desk and the cabinet.

A simple way to check: if both parts of the sentence could stand alone as complete sentences, add a comma. If not, skip it.

Rule 4: Use Commas Around Nonessential Information

A comma is used to separate extra information in a sentence—details that add meaning but aren’t necessary for identifying the subject or completing the idea. These added words or phrases are called nonessential (or nonrestrictive) because the sentence would still make perfect sense without them.

Commas on both sides act like brackets. They show that the information between them can be removed without changing the main point.

Example: My sister, who lives in Vancouver, is visiting next week.

If you remove who lives in Vancouver, the sentence still reads clearly: My sister is visiting next week. The commas signal that the added phrase is helpful but not crucial.

In contrast, essential information (restrictive clause) identifies which person or thing you’re talking about. In that case, you don’t use commas.

Example: The students who arrived early got front-row seats.

Here, the phrase who arrived early is essential. It tells you which students, so no commas are used.

Nonessential caluse or information often includes names, descriptions, or side notes that clarify or add personality to writing:

• The museum, built over a century ago, still attracts thousands of visitors.
• Mr. Davis, our history teacher, loves ancient civilizations.
• The old bridge, damaged during the storm, is being restored.

A quick check: if removing the phrase doesn’t change who or what you’re talking about, use commas. If it does, skip them.

Rule 5: Use a Comma Between Coordinate Adjectives

When two or more adjectives describe the same noun equally, they’re called coordinate adjectives. In this case, you should place a comma between them to make the description flow naturally.

A simple way to test whether adjectives are coordinate is to try adding the word and between them or reversing their order. If the sentence still sounds natural, a comma belongs there.

Examples:

• It was a long, exhausting meeting. (A long and exhausting meeting — makes sense.)
• She gave a thoughtful, generous response. (A generous, thoughtful response — also correct.)

Both adjectives describe the noun independently, so the comma helps separate them clearly. However, if the adjectives build upon each other and must appear in a specific order, then no comma is needed. These are called cumulative adjectives. Each one modifies the next, forming a single description.

Examples:

• He wore a bright red jacket. (Not “red bright jacket.”)
• They live in a small wooden cabin. (Not “wooden small cabin.”)
• She found an old leather notebook. (Not “leather old notebook.”)

You can’t swap these adjectives or add and between them naturally, so commas are omitted.

Rule 6: Use a Comma for Direct Address, Tag Questions, and Interjections

A comma helps separate words or phrases that stand apart from the main sentence—like when you speak directly to someone, add a quick question at the end, or insert a short emotional word or reaction. These elements don’t change the sentence’s core meaning, but they guide tone and rhythm for the reader.

When addressing someone directly, a comma sets the name or title apart to show who’s being spoken to.

Examples:

• Emma, could you send me that file?
• Thank you, Professor, for your guidance.
• Please take a seat, everyone.

Without the comma, sentences like Let’s eat grandma and Let’s eat, grandma take on completely different meanings—one funny, one alarming.

Commas also appear in tag questions, the small prompts added to the end of a sentence to confirm information or seek agreement.

Examples:

• It’s quite cold today, isn’t it?
• You’ve finished the assignment, right?

In these cases, the comma marks a natural pause before the short question that turns a statement into a gentle check or confirmation.

Finally, interjections—quick expressions such as oh, well, yes, no, or indeed—use commas to separate emotion or reaction from the rest of the sentence.

Examples:

• Oh, I didn’t see you there.
• Yes, that makes perfect sense.
• Well, I suppose we’ll try again tomorrow.

Rule 7: Use a Comma in Dates, Numbers, and Addresses

Commas play an important role in keeping long numbers, dates, and addresses readable. They help break information into smaller parts, so readers can process it quickly without confusion.

When writing dates, a comma separates the day, month, and year to show the correct order. In American English, the comma comes after the day and also after the year when the sentence continues.

Examples:

• The event will be held on June 14, 2025, at the convention center.
• She was born on October 3, 1998, in Chicago.

In British English, the day usually comes before the month, and no comma is needed: 14 June 2025.

For numbers, commas divide large figures into groups of three digits, starting from the right. This makes them easier to read and prevents mistakes.

Examples:

• 1,000 (one thousand)
• 25,600 (twenty-five thousand six hundred)
• 3,456,782 (three million four hundred fifty-six thousand seven hundred eighty-two)

When writing addresses, commas separate each part—the street, city, state or region, and country.

Examples:

• 245 Oakwood Avenue, Boston, Massachusetts, USA
• 17 Green Street, Bristol, England

If the sentence continues after the address, add another comma before resuming the main clause: He moved to 245 Oakwood Avenue, Boston, Massachusetts, USA, last summer.

Avoiding Comma Splices (When a Comma Isn’t Enough)

A comma splice happens when two complete sentences are joined only with a comma. Although each part could stand alone, the comma by itself isn’t strong enough to hold them together. This makes the sentence grammatically incorrect and sometimes confusing to read.

Incorrect: ❌ The storm was intense, the streets started flooding.

The problem here is that both halves — The storm was intense and the streets started flooding — are independent clauses. A comma creates too weak a link between them.

To fix a comma splice, you have a few clear options:

• Use a period to separate the sentences: The storm was intense. The streets started flooding.
• Use a semicolon to connect related ideas: The storm was intense; the streets started flooding.
• Use a coordinating conjunction (FANBOYS) after the comma: The storm was intense, and the streets started flooding.

Each correction is grammatically sound, but the best choice depends on how closely related the ideas are. If the thoughts belong together, a semicolon or conjunction keeps the flow. If not, a period gives them more weight and independence.

Quick Comma Reference: Rules and Examples

Here’s a simple reference chart that sums up the main comma rules in English grammar. Use it as a quick reminder when editing or reviewing your writing.

Frequently Asked Questions (FAQs)