Comma Rules and Usage With Examples

The comma is used more than any other punctuation in writing. Because of this, there are many misinterpretations of where a comma belongs, rule misuses, and myths provided by poor teaching practices. 

No, you do not use a comma anytime you take a breath when reading a sentence, but a comma does designate a pause. Take a look at how you should use commas to help separate essential elements and make your writing clear and concise. 

What is the Use of a Comma?

A comma [,] tells a reader to take a short pause before continuing with reading. It separates basic elements and is used to set off added details and features within a sentence. Without commas, sentences would jumble words together and create confusion surrounding the importance of specific information. 

How To Use Commas With Compound Sentences

A compound sentence is when two or more independent clauses are joined by a coordinating conjunction such as and, but, for, or, nor, so, or yet. A comma is needed to separate the independent clauses and is an essential punctuation mark when used. 

For Example:

  • The storm clouds were gathering, so we moved our picnic under shelter.

Examples of When NOT to Use a Comma With a Conjunction 

Do not make the error of automatically inserting a comma when you see a conjunction. Coordinating conjunctions also join compound subjects, verbs, prepositional phrases, and clauses. Not all require the use of a comma. 

Compound SubjectThe students and the parents met with the teachers last night. 
Compound VerbWe love to swim and hike when on vacation. 
To Prepositional PhrasesI threw the baseball to the catcher and to the second baseman. 
Two Subordinate ClausesMy children love to read books only if the material is exciting and only if the pages have pictures. 

How to Use Commas When Listing Three Things

Use commas to separate three or more words, prepositional phrases, or clauses within a sentence. This use is called a serial comma or Oxford comma and helps avoid confusion when more than one thing is used in a list. See further examples of that here: How to Use Oxford Commas

WordsI read through all my handouts, the textbook, and classroom notes when preparing for the exam. 
Prepositional PhrasesScotland has been shaped by its geography, by its people, and by its heritage. 
ClausesThere is proof that the Americas were settled by tribes that traveled across the Bearing Straits, the Vikings who came by boat, and later by Europeans searching for a passage to India. 

It is permissible to omit the last comma in a series as long as this pattern is followed throughout the material and does not create confusion.  

Examples of When NOT to Use a Comma In a Series

Commas are not needed if conjunctions separate all the items in a series. 

For Example: 

  • I sliced and folded and placed the apples in the muffin tins to bake. 

Commas are not needed to separate pairs of items listed together within a sentence.

For Example:

  • I asked for bacon and eggs, toast and jam, and coffee and cream. 

How to Use Commas to Separate Coordinate Adjectives

Commas divide adjectives of equal rank. These are called coordinator adjectives and are defined using two simple rules: 

  • You can place an and between the adjectives in a sentence, and it retains the exact same meaning AND
  • You can switch the adjectives, and it still sounds grammatically correct. 

For Example:

  • I left detailed, precise lesson plans for my students to follow when I was gone. 

Do NOT Use Commas to Separate Cumulative Adjectives

Cumulative adjectives must stay in the order they are given to avoid confusing the sentence. You do not use commas between adjectives that must remain in a specific order. 

For Example:

  • The cast system of Middle Age European countries had rigid social classes.  

How to Use Commas After Introductory Material

Commas are used after introductory words, phrases, or clauses. This usage allows readers to recognize that the initial information has come to a close and that the main part of the sentence will follow. Look at the following examples to help you:

Words

Introductory Words

  • Yes, I would be happy to help you weed your garden this weekend. 

Nouns of Direct Address

  • Doug, please stay after class for help. 

Common Expressions/Interjections

  • Of course, we can get that schedule finalized for you. 

Introductory Adverbs

  • Obviously, he had worked very hard on the project and received a passing grade. 

Phrases

Prepositional Phrases

  • In the deep recesses of the tidal pool, the tiny crabs were hiding from predators.

Participial Phrases

  • Jumping over the fence, my son caught and ripped his pants. 

Infinitive Phrases

  • To get to school on time, we had to catch the bus by 7 am. 

Clauses

Adverb Clauses

  • When the potatoes began to brown, we took them off the stovetop. 

How to Use Commas With Parenthetical Expressions

A parenthetical expression is a word or phrase that interrupts the flow of a sentence. Commas help offset the expression to provide clarity. 

ExpressionsExamplesIn a Sentence
Nouns of Direct AddressTim, Mr. Clements, my son, sweetheartWe will leave, Micheal, as soon as the train arrives. 
Conjunctive Adverbsbesides, also, however, furthermore, indeed, moreover, instead, otherwise, nevertheless, thus, thereforeThe dogs, however, refused to get out of the muddy puddle, and all received a bath later that night. 
Common Expressions/Interjectionsin my opinion, of course, on the other hand, by the way, I feel, in the first placeHer garden, by the way, is full of heritage blooms she has cultured from seeds. 
Contrasting ExpressionsNot mine, not there, not that oneIt was hers, not mine, which is why you were confused in the first place. 

How to Use Commas with Nonessential Expressions

Nonessential expressions are added information that is not needed for a reader to understand the meaning of a sentence. It provides additional detail but will not change the sentence meaning if removed. Commas are required to help offset the expression since it interrupts the flow of a sentence.

Essential vs. Nonessential Expressions

It is important to recognize the difference between an essential and nonessential expression. Commas are not used with essential expressions because they provide necessary information in a sentence. Removing essential expressions from a sentence changes the meaning. 

Essential Expression ExamplesNonessential Expression Examples
The child holding the teddy bear is boarding the plane.Jonathon Ayers, holding the teddy bear, is boarding the plane. 
The famous actor Michael Smith has won many awards.Michael Smith, a famous actor, has won many awards. 

Other Uses of Commas

Commas are used in everyday writing scenarios concerning technical communication and correspondence, formatting materials, and even addresses. The following examples help provide you with their proper use in various situations to ensure there is no confusion.

Using Commas With Location

When citing a specific place or geographical location made up of two or more places, a comma is necessary to separate each item. 

For Example:

  • I traveled from Hobbs, New Mexico, to Dallas, Texas, to catch a plane. 

Using Commas With Dates

When a date includes two or more parts, use a comma after each item. An exception to this rule is when you use a month followed by a day or a year. 

For Example:

  • The assignment was due on Monday, April 26, and had to be turned in online. 
  • The class trip to Greece departs on November 16, 2023.
  • The rain was steady through March 2018. 

Using Commas With Titles

When a name is followed by one or more commas, use a comma after the name and after each title. 

For Example:

  • I saw that Joe Smith, Sr., was the lead salesman for June. 

Using Commas With Addresses

An address that consists of two or more parts requires commas to separate each part. Avoid using commas if prepositions join the parts of an address. 

For Example:

  • Sarah’s new address is 1615 South Opal, Oxford, Tennesse 65431.
  • Sarah’s new address is on South Opal in Oxford. 

Using Commas With Salutations and Closings

Commas follow all salutations and closings in a letter. 

SalutationsDear Mr. Smith,  Dear Aunt Sarah, Dear Mr. and Mrs. Jonathon Swift,  Dear Monica, 
ClosingsSincerely,  Yours Truly,  Respectively,  In Appreciation,  Regards,                             

Using Commas With Numbers

Numbers that have more than three digits require the use of a comma after every third digit from the right to designate place. 

For Example:

  • The new hotel can comfortably host up to 12,640 people. 
  • The candy shop sold over 1,500,000 boxes of chocolate for Valentine’s Day. 

When NOT to Use a Comma With Numbers

There are some exceptions to this rule. Do not use a comma with the following:

Zip Code48009
Telephone Numbers(716) 555-2020
Page NumbersPage 4306
House Numbers19257 North Lamson
Serial/Tracking/Social Security Numbers154 05 3007 24576

Using Commas With Omissions

Words and phrases may be purposely omitted from a sentence to create an elliptical sentence. An elliptical sentence structure implies omitted words by using other elements within the sentence. To provide clarity, insert a comma where words have been left out as a visual clue that an omission exists. 

For Example:

  • The child walked quickly, and the babysitter, slowly

Using Commas With a Direct Quotation

Commas are used to set off direct quotations from the rest of the sentence.

For Example:

  • “If you don’t mind the added time,” the tour guide told us, ”we can stop in the next town for some sightseeing before heading to the hotel.”

Let’s Review

Understanding the proper use of commas can help you avoid making careless mistakes that may change the meaning of your sentences. Overuse of commas is common, as is poor placement. Even though they might not create problems overall with your message, you want your writing to sound sophisticated and polished to your readers.