How to use commas: rules and examples

OK, we might be exaggerating a little bit, but a misplaced comma can lead to confusion and hilarious misunderstandings. For example, “Let’s eat Grandpa!” has a completely different meaning from “Let’s eat, Grandpa!” 

A well-placed comma adds clarity to your sentences. A comma is a versatile punctuation mark, which is why it often gets misused. The comma helps you separate words, phrases, and ideas within a sentence. It represents a small pause or break. 

With such varied uses, it’s easy for even the most grammar-savvy person to get confused sometimes. In this post, we explain the different types of commas, some critical grammar rules, and how to use commas in your writing to prevent you from misusing this common punctuation mark.

4 types of commas

When trying to decide if your sentence needs a comma, it can help to think about four types, or common uses, of commas. 

1. Interrupter or bracketing commas

Sometimes sentences have interruptions, or little thoughts, in the middle of the sentence. These interruptions should be bracketed by commas, with a comma before and after the interruption. 

Interrupter commas help the flow of the sentence and add clarity. You can often find where interrupter or bracketing commas are needed by reading the sentence aloud. Some common interrupter words and phrases include: however, unfortunately, in fact, needless to say, therefore, and sadly.

2. Conjunction commas

Place a comma before the conjunction when combining two independent clauses with a conjunction. Conjunctions include and, but, and or. 

Does this mean you always put a comma after a conjunction? No! Remember, this rule applies when you’re joining together two independent or main clauses. 

3. Introductory commas

You use an introductory comma after a clause, phrase, or word at the start of a sentence. This phrase is a dependent clause that doesn’t act as a whole sentence.

4. Serial commas

When you’re writing a list or series of elements containing three or more items, you use a serial comma (aka. Oxford Comma) after each entry to make it easy to read and understand.  

In the incorrect example, there are no commas, which makes it hard to read the list. There always should be a comma after eggs and bacon. 

However, there is a debate on whether you need a comma after toast. If you’re using a serial comma, you add a comma before the last conjunction in your list, as in the example above. 

Using the serial comma is generally a matter of choice unless you must follow a set styleguide. Styleguides that require the serial comma include the Oxford Style Manual, Chicago Manual of Style, and the MLA Style Manual. The AP Style Guide doesn’t require the serial comma. You should also use it in situations where there is ambiguity, as in the above example. 

The 8 rules for commas

Commas have many uses. It can be helpful to keep these eight rules in mind so you can use them correctly.

1. Use a comma when addressing a person 

When the speaker in the sentence addresses the audience by name, it’s called a direct address. 

2. Use a comma with a question tag

Question tags are often used in sentences when the author is trying to get readers to agree with the statement. In this case, place the comma before the question tag.

3. Use a comma with nonessential appositives

An appositive is a noun, pronoun, or phrase beside another noun or pronoun in the sentence that helps explain or identify it. A nonessential appositive can be removed without it changing the meaning of the sentence. In this case, the nonessential appositive word or phrase should be set off with commas.

4. Use a comma with direct quotations 

Use a comma to introduce dialogue. When you have a phrase like “she said” that identifies the speaker of the dialogue or quote, you use a comma to separate the phrase from the quote. The phrase, called an attributive tag, can come after, before, or in the middle of the quote.

5. Use a comma inside quotation marks

In American English, use a comma before closing a quotation mark.

6. Use commas with nonrestrictive clauses

Nonrestrictive clauses are clauses that aren’t essential to the meaning of the sentence. 

7. Use a comma to separate coordinate adjectives

Coordinate adjectives are two or more adjectives working together to modify the same noun. Coordinate adjectives still make sense if you place the word and between them or change the order. The adjectives are roughly equal in importance. 

8. Using a comma with dates

Use a comma to separate the month and day from the year.

Use a comma when you reference a day of the week and a date.

You don’t need a comma if you use the day-month-year format or refer only to a month and year.

How to use commas in your writing

When you’re writing, it can help to keep in mind situations when you don’t need a comma. Here are some ways commas are often misused. 

Look out for a comma splice

A comma splice occurs when you have a comma between two independent clauses without a conjunction. You can fix this mistake by either adding a conjunction, making each independent clause its own sentence, or replacing the comma with a semicolon.

Don’t automatically put a comma before “but”

You only need a comma before but when you’re connecting two independent clauses.

You don’t need a comma before but when you have one independent clause and one dependent clause.

Avoid putting a comma before that in a restrictive clause

The word that is often used to introduce a restrictive clause. In those situations, you don’t need a comma.

Don’t use a comma if the sentence’s dependent clause follows the independent clause

While you should use a comma when the dependent clause comes at the start of the sentence, you shouldn’t use a comma when it comes after the independent clause.

In sum, commas help add clarity to your writing. While they add a short pause or break, you don’t need one every time you naturally pause in a sentence. Using that strategy can result in too many commas. Yet, there are specific rules and guidelines to help you know when a comma is needed.

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