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This handout offers seven easy steps to becoming a comma superhero.
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:
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.
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:
There are medium introductory bits. Often these are two- to four-word prepositional phrases or brief -ing and -ed phrases:
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:
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.
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.
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.)
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.
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:
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.
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.
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.
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. These commas help your reader figure out your main point by telling him or her that the words within the commas are not necessary to understand the rest of the sentence. In other words, you should be able to take out the section framed by commas and still have a complete and clear sentence.
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.
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.
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 the original version of 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 the latest publications on this topic. 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.
Rosen, Leonard J. et al. The Allyn & Bacon Handbook. Boston: Allyn & Bacon, 2000.
Gordon, Karen Elizabeth. The Deluxe Transitive Vampire: The Ultimate Handbook of Grammar for the Innocent, the Eager, and the Doomed. New York: Pantheon Books, 1993.
Gordon, Karen Elizabeth. The New Well-Tempered Sentence. Boston: Houghton Mifflin Company, 1993.
Kolln, Martha. Understanding English Grammar. New York: MacMillan Publishing Company, 2005.
Kolln, Martha. Rhetorical Grammar: Grammatical Choices, Rhetorical Effects. New York: MacMillan Publishing Company, 2006.
O’Conner, Patricia T. Woe Is I. New York: Riverhead Books, 2003.
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