What this handout is about
In English, commas are used to separate parts of sentences. Use a comma to separate elements of a list, distinguish groups of words that go together, mark conjunctions between complete thoughts, and more. This handout offers seven easy steps to deciding when to use a comma.
Commas, commas, and more commas
Commas help your reader figure out which words go together in a sentence and which parts of your sentences are most important. Using commas incorrectly may confuse the reader, signal ignorance of writing rules, or indicate carelessness. Although using commas correctly may seem mysterious, it can be easy if you follow a few guidelines.
Beware of popular myths of comma usage:
- MYTH: Long sentences need a comma. A really long sentence may be perfectly correct without commas. The length of a sentence does not determine whether you need a comma.
- MYTH: You should add a comma wherever you pause. Where you pause or breathe in a sentence does not reliably indicate where a comma belongs. Different readers pause or breathe in different places.
- MYTH: Commas are so mysterious that it’s impossible to figure out where they belong! Some rules are flexible, but most of the time, commas belong in very predictable places. You can learn to identify many of those places using the tips in this handout.
You probably already know at least one of the following guidelines and just have to practice the others. These guidelines are basically all you need to know; if you learn them once, you’re set for most situations.
1. Introductory bits (small-medium-large)
Setting off introductory words, phrases, or clauses with a comma lets the reader know that the main subject and main verb of the sentence come later. There are basically three kinds of introductory bits: small, medium, and large ones. No matter what size they are, an introductory bit cannot stand alone as a complete thought. It simply introduces the main subject and verb.
There are small (just one word) introductory bits:
Generally, extraterrestrials are friendly and helpful.
Moreover, some will knit booties for you if you ask nicely.
There are medium introductory bits. Often these are two- to four-word prepositional phrases or brief -ing and -ed phrases:
In fact, Godzilla is just a misunderstood teen lizard of giant proportions.
Throughout his early life, he felt a strong affinity with a playful dolphin named Flipper.
Frankly speaking, Godzilla wanted to play the same kinds of roles that Flipper was given.
Dissatisfied with destruction, he was hoping to frolick in the waves with his Hollywood friends.
There are large introductory bits (more than 4 words). You can often spot these by looking for key words/groups such as although, if, as, in order to, and when:
If you discover that you feel nauseated, then you know you’ve tried my Clam Surprise.
As far as I am concerned, it is the best dish for dispatching unwanted guests.
FANBOYS is a handy mnemonic device for remembering the coordinating conjunctions: For, And, Nor, But, Or, Yet, So. These words function as connectors. They can connect words, phrases, and clauses, like this:
Words: I am almost dressed and ready.
Phrases: My socks are in the living room or under my bed.
Clauses: They smell really bad, so they will be easy to find.
Notice the comma in the final example. You should always have a comma before FANBOYS that join two independent clauses (two subjects and two verbs that make up two complete thoughts). Look carefully at the next two sentences to see two independent clauses separated by comma + FANBOYS.
If you do not have two subjects and two verbs separated by the FANBOYS, you do not need to insert the comma before the FANBOYS. In other words, if the second grouping of words isn’t a complete thought, don’t use a comma. Try reading the words after FANBOYS all by themselves. Do they make a complete thought?
You can read your own writing in the same way. Read what comes after FANBOYS all by itself. If it’s a complete thought, you need a comma. If not, you don’t.
3. The dreaded comma splice
If you don’t have FANBOYS between the two complete and separate thoughts, using a comma alone causes a “comma splice” or “fused sentence” (some instructors may call it a run-on). Some readers (especially professors) will think of this as a serious error.
BAD: My hamster loved to play, I gave him a hula-hoop.
ALSO BAD: You wore a lovely hat, it was your only defense.
To fix these comma splices, you can do one of four simple things: just add FANBOYS, change the comma to a semicolon, make each clause a separate sentence, or add a subordinator (a word like because, while, although, if, when, since, etc.)
GOOD: You wore a lovely hat, for it was your only defense.
ALSO GOOD: You wore a lovely hat; it was your only defense.
STILL GOOD: You wore a lovely hat. It was your only defense.
TOTALLY GOOD: You wore a lovely hat because it was your only defense.
4. FANBOYS fakers
However, therefore, moreover, and other words like them are not FANBOYS (they are called conjunctive adverbs). They go between two complete thoughts, just like FANBOYS, but they take different punctuation. Why? Who cares? You just need to recognize that they are not FANBOYS (for, and, nor, but, or, yet, so—remember?), and you’ll make the right choice.
When you want to use one of these words, you have two good choices. Check to see if you have a complete thought on both sides of the “conjunctive adverb.” If you do, then you can use a period to make two sentences, or you can use a semicolon after the first complete thought. Either way, you’ll use a comma after the faker in the second complete thought. Notice the subtle differences in punctuation here:
GOOD: Basketball is my favorite sport. However, table tennis is where I excel.
ALSO GOOD: Basketball is my favorite sport; however, table tennis is where I excel.
BAD: Basketball is my favorite sport, however table tennis is where I excel.
ALSO BAD: Basketball is my favorite sport, however, table tennis is where I excel.
5. X,Y, and Z
Put commas between items in a list. When giving a short and simple list of things in a sentence, the last comma (right before the conjunction–usually and or or) is optional, but it is never wrong. If the items in the list are longer and more complicated, you should always place a final comma before the conjunction.
EITHER: You can buy life, liberty, and the pursuit of happiness in Los Angeles.
OR:You can buy life, liberty and the pursuit of happiness in Los Angeles.
BUT ALWAYS: A good student listens to his teachers without yawning, reads once in a while, and writes papers before they are due.
If you have two or more adjectives (words that describe) that are not joined by a conjunction (usually and) and both/all adjectives modify the same word, put a comma between them.
He was a bashful, dopey, sleepy dwarf.
The frothy, radiant princess kissed the putrid, vile frog.
Two commas can be used to set off additional information that appears within the sentence but is separate from the primary subject and verb of the sentence. Sometimes called a “parenthetical expression” or an “aside,” this information interrupts the main thought to add an additional comment. Occasionally, the interrupter won’t actually interrupt the main thought. It may be added at the end. In that case, it’s preceded by a comma and followed by a period.
Bob Mills, a sophomore from Raleigh, was the only North Carolina native at the Japanese food festival in Cary.
Aaron thought he could see the future, not the past, in the wrinkles on his skin.
My chemistry book, which weighs about 100 pounds, has some really great examples.
The organization is committed to protecting wildlife, especially pandas.
To see if you need commas around an interrupter, try taking the interrupter out of the sentence completely. If the sentence is still clear without the interrupter, then you probably need the commas.
Congratulations! You know how to use commas!
But wait—is there more?
These guidelines cover the most common situations in writing, but you may have a stickier question. Below are some suggestions for finding some of the many other resources at your disposal.
If you are worried about punctuation in general, pick up a writing handbook from the library or the University bookstore. You’ll find a list of handy resources below.
We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial. We revise these tips periodically and welcome feedback.
Gordon, Karen. 1993. The Deluxe Transitive Vampire: The Ultimate Handbook of Grammar for the Innocent, the Eager, and the Doomed. New York: Pantheon Books.
Gordon, Karen. 1993. The New Well-Tempered Sentence: A Punctuation Handbook for the Innocent, the Eager, and the Doomed. Boston: Houghton Mifflin Company.
Kolln, Martha, and Loretta Gray. 2016. Rhetorical Grammar: Grammatical Choices, Rhetorical Effects, 8th ed. Boston: Pearson Education.
Kolln, Martha, Loretta Gray, and Joseph Salvatore. 2016. Understanding English Grammar, 10th ed. Boston: Pearson Education.
O’Conner, Patricia. 2010. Woe Is I: The Grammarphobe’s Guide to Better English in Plain English, 3rd ed. New York: Penguin Publishing Group.
Rosen, Leonard J., and Laurence Behrens. 2003. The Allyn & Bacon Handbook, 5th ed. New York: Longman.
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