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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.
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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.
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2. FANBOYS
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.
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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.
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4. FANBOY fakers
However, therefore, moreover, and other words like them are not FANBOYS (they are called conjunctive adverbs). They go between t