Commas are everywhere, so knowing where they go in a sentence should be easy, right? Wrong.
Commas have rules about where they can and cannot be used in a sentence (although, there are some exceptions). You can use commas to separate clauses, set apart added information, show items in a series or to ease confusion in a sentence.
Here’s a (not so) quick lesson on comma use.
With Coordinating Conjunctions
Use a comma with a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so) to separate independent clauses.
For example:
The penguin always dreamed of being a basketball star, but a two–foot–tall flightless bird just can’t dunk.
Note: If the two independent clauses are very short and there is no chance the separate thoughts without the comma would be confusing, you may omit the comma.
They see me rollin’ and they hatin’.
With Subordinating Conjunctions
When a sentence begins with a subordinating conjunction, use a comma after the subordinate clause.
For example:
Before she became a respected judge, Sheila was a professional knife thrower in the circus.
After an Introductory Clause
Use a comma after an introductory clause, phrase or word that comes before the main clause in the sentence or after “if clauses.”
For example:
To save money, I make my own toilet paper out of lawn trimmings and dried leaves.
Having just eaten the entire 72 oz. steak, Harold had no appetite for ice cream during our drive home from the restaurant.
Unlike the other members of the band, Mike never minded wearing the required sequined unitard.
If you need any help moving this weekend, please call someone else.
With Non-Essential Internal Clauses
Use a pair of commas within the sentence to set off clauses, phrases or words that are not essential to the meaning of the sentence. If you can remove the information and the sentence still makes sense, then use commas at the beginning and end of the clause, phrase or words to set the words apart from the rest of the sentence.
For example:
Sam’s car, as far as I can tell, was modeled after the 1960’s Batmobile.
My apartment, though shabby and roach–filled, is within walking distance to my work.
Note: Use commas to set apart names and identifying information only when it is not an essential element to the sentence. If the reader does not need the information for the sentence to make sense or to correctly identify the people or things in question, then place the information between commas.
For example:
Leia’s twin brother, Luke, was raised on Tatooine by his aunt and uncle.
My English teacher, Mr. Baker, is growing a little tired of receiving my Fraggle Rock fan fiction stories instead of my assignments.
In these examples, the information between the commas is not necessary for the reader to understand the sentence or identify the subjects of the sentences. In the first example, Leia has only one twin brother, so his name is not necessary to the sentence. In the second example, the writer has only one English teacher, so the teacher’s name can be set apart as well as the reader does not need the name for proper identification.
Essential Elements and Necessary Information
Do not use a comma to set apart information that is necessary for the sentence to make sense, such as clauses beginning with that or which. Also, do not use commas to set apart names and personal information if the reader needs the information for correct identification.
For example:
Foods that are high in fat are usually delicious.
My teacher Ms. Wilson loves my Fraggle Rock fan fiction and squeals with excitement when I give her my new chapters to read.
In the first example, the clause that are high in fat is necessary to understanding the sentence, so it is not set apart with commas. In the second example, the name Ms. Wilson is necessary to identifying the writer’s teacher, as there is no other identifying information given for the reader to discern which teacher the writer is referring to.
Lists and Items in a Series
Use commas to separate three or more words, phrases or clauses in a series.
For example:
I brought balloons, chips and a live mongoose to the party.
The candidate promised lower taxes, better schools and free doughnuts on everyone’s birthday.
The Oxford Comma
At one time, grammar rules stated that you needed a comma between the penultimate list item and the concluding conjunction (usually and). However,the current guidance is to omit the last comma, unless leaving it out would cause confusion to the reader.
For example:
I have the greatest respect for my parents, Abraham Lincoln and Gandhi.
You can see how many readers might be confused by thins sentence. You have two options to rewrite the sentence so it makes more sense:
I have the greatest respect for my parents, Abraham Lincoln, and Gandhi.
or
I have the greatest respect for Abraham Lincoln, Gandhi and my parents.
Lists containing items with internal conjunction may require an additional comma to make sense.
For example:
My favorite sandwich toppings are egg salad, ham and cheese, and peanut butter and jelly.
With Coordinating Adjectives
Use commas to separate two or more coordinating adjectives that describe the same thing. Do not use a comma between the final adjective and the noun or between non-coordinating/cumulative adjectives.
Note on adjectives: Coordinating adjectives can be written in any order; the meaning of the sentence stays the same regardless of the adjectives’ order. If you can place and between the adjectives and it still makes sense, they are coordinating adjectives. Cumulative adjectives, however, must be written in a specific order to make sense or to sound correct. They cannot be rearranged and thus do not have the comma between them.
For example:
My pet tortoise is affectionate, loyal and surprisingly fast.
In this example, the sentence would still make sense if the adjectives were moved around (i.e., surprisingly fast, loyal and affectionate and loyal, surprisingly fast and affectionate still sound right and make sense) or if you substituted the commas with the word and (affectionate and loyal and surprisingly fast).
The robbers completely missed the unmarked police car sitting outside the bank.
In this example, you cannot move around the adjectives. Police unmarked car and unmarked and police car don’t sound correct or make sense, so you would not use a comma between the adjectives.
Shifts in Mood and Contrasting Elements
Use a comma to as a pause to indicate a shift in the mood or contrasting ideas.
For example:
The octopus’s ability to open locks was extraordinary, almost human.
I always tell you the truth, don’t I?
Phrases That Refer Back to the Beginning of the Sentence
Use a comma to set apart phrases that refer back to the beginning or middle of the sentence.
For example:
The clown waved at the children, cackling ominously.
Geographical Names, Dates, Numbers and Professional Titles
Use commas to set apart geographical names, years in dates, numbers above 1,000 and professional titles.
For example:
Xavier’s School for Gifted Youngsters is located outside of Salem Center, New York.
Frodo Baggins was born on September 22, 2968 of the Third Age of MIddle Earth.
The mountaineers began seeing yeti tracks when they reached 12,771 feet in elevation.
Steven Strange, M.D., is highly skilled in neurosurgery and the mystic arts.
Quotations and Dialogue
Use commas to separate dialogue or quotations within a body of text or set apart text written within the quotation.
For example:
My grandmother took one look at my haircut and said, “Well, bless your heart.”
“I always try and visit Death Valley in the summertime,” said the tourist covered in sunburn and sweat, “because I hate fighting the crowds.”
Interrogative Tags, Minor Interjections and Direct Addresses
Use a comma to set off direct addresses, interjections like yes, no and oh and interrogative tags.
For example:
Let’s eat, Grandma.
Well, I certainly didn’t expect the Spanish Inquisition.
Yes, I was out all night and came home painted blue, but there’s nothing to be alarmed about.
No, we don’t need to discuss how the llama got into the backseat of my car.
Oh, you shouldn’t have!
Suddenly, the Kool-Aid man burst through the wall, shouting, “Oh, yeah!”
After i.e. or e.g.
The abbreviations i.e. (id est or in other words) and e.g. (exempli gratia or for example) should always be followed by a comma.
For example:
My teacher returned my paper with a failing grade, saying that I had not followed her instructions, i.e., instead of writing about the Industrial Revolution, I wrote about mermaids.
Although mermaids are my favorite subject, I do enjoy writing about other cryptids (e.g., Bigfoot, El Chupacabra and the Mongolian death worm).
Preventing Confusion
Sometimes a comma is necessary to prevent or ease reader confusion.
For example:
What we were afraid would happen, happened.
Those who can’t, shouldn’t.
I wish I had, had I known what the consequences would be.
When to NOT Use a Comma
- Between a subject and verb
- Between an adjective and noun
- Between an adverb and adjective
- After a coordinating conjunction
- After such as or like.
- Directly before or after a question mark or exclamation point
- Between compound elements that are not independent clauses
The Dreaded Comma Splice
One thing you must always be wary of in your writing is incorrectly using just a comma between two independent clauses and creating a comma splice. Independent clauses must be joined together with a comma and a conjunction or separated with a semicolon or period.
For example:
Darcy couldn’t wait to go on vacation, the last time she took a trip was when she went to the International Yo-yo Museum two years ago.
is a comma splice and should be written as:
Darcy couldn’t wait to go on vacation, since the last time she took a trip was when she went to the International Yo-yo Museum two years ago.
or
Darcy couldn’t wait to go on vacation; the last time she took a trip was when she went to the International Yo-yo Museum two years ago.
or
Darcy couldn’t wait to go on vacation. The last time she took a trip was when she went to the International Yo-yo Museum two years ago.
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