By now, you’ve surely heard of the most expensive comma in Canada. One party canceled a contract that the other party thought was firmly in place for at least five years. According to the contract’s terms, it was to continue in force "for a period of five years from the date it is made, and thereafter for successive five year terms, unless and until terminated by one year prior notice in writing by either party."

The second comma caused the problem. Without it, both sides were locked into at least a five-year deal. With it, either party could cancel the contract at any time with prior notice of just one year. Of course, that’s what happened. The extra comma cost the losing party about $2 million.

Are your commas each worth $2 million? Maybe not, but commas are important to clear and effective writing. Just what can commas do?

Fence Off Fluff – YES
Sometimes our sentences have interesting, but not crucial, fluff. The fluff is mildly helpful or entertaining (or we’d have edited it out long ago). But it’s not really that important. Commas fence off the fluff.

Example: The defendant, who looked apologetic, was found guilty.

The key to the sentence is that the defendant was found guilty. It’s interesting that she looked apologetic, but that fact didn’t change her guilt. The reader could skip over the fenced-off fluff and still know the key fact from the sentence.

Note what happens to our example when the commas disappear.

Example: The defendant who looked apologetic was found guilty.

This sentence suggests that there were two defendants. The one who looked apologetic was found guilty, while the other one went free.

End Introductions – YES
If a sentence begins with a wind-up introduction (like this one), the reader needs to know when that introduction is over and the real sentence begins. Typically, introductions of four words or more need to end with commas. Otherwise, the poor reader isn’t sure when to make the mental transition from wind-up to pitch.

Note the possible confusion in the following example: As we sat eating the cows
mooed softly. Did you have a mental image of eating cows before you realized that we were eating a vegan delight and the happy cows were mooing in the background? A comma after "eating" would have avoided any question about whether the cows were on the menu.

Clarify Lists – YES
Curmudgeons love the "Oxford" comma that always comes before "and" in lists. Our flag is red, white, and blue. We know that magazines and newspapers are more concerned with line space than patriotism, so their flags are red, white and blue (without the lovely last comma).

But even non-curmudgeons appreciate commas to clarify some lists.

Example: For lunch, I like to eat a small apple, a sandwich with peanut butter and jelly and ice cream.

Is the ice cream on the sandwich? Of course not, but the sentence painted a gastronomic disaster before your brain sorted things out. A little comma right after "jelly" could have separated my lunch into three clear courses: an apple appetizer, a sandwich, and dessert.

Split Lists of Two – NO
The following rant is not really about what a comma can’t do, but rather what we should never force a comma to do. When a list has just two items in it, please do not separate the two by a comma.

When the two items are short and come close together in the sentence, we have little inclination to insert commas. No one would use a comma in the following example: "My daughter plays soccer and basketball." The urge to add a comma comes when each item has its own little entourage: "My daughter plays goalie on the little league soccer team and point guard on the elementary school basketball team." Some of you were tempted to insert a comma before "and." Resist the urge.

Incorrect: The attorney read the demand letter, and called the client.
In this sentence, the attorney did two things—he read and called. Those two verbs should not be separated by a comma. Note that if the attorney did more than two things, the commas would come rushing back. "The attorney read the demand letter, called the client, and began drafting a response."

There is an exception: you can use a comma to avoid confusion between two items in a long list. For example: "My daughter plays goalie on the little league soccer team and point guard on the elementary school basketball team, and is the first violin in the youth orchestra." Of course, that many activities may deserve two complete sentences.

Certainly the Canadian example would have benefited from a period and a new sentence. Watch how much clearer the contract’s terms become with polished punctuation: "This contract will be in force for a period of five years from the date it is made. After that five-year period, the contract will continue for successive five-year terms, unless and until terminated by one year prior notice in writing by either party."

Separate Subjects and Verbs – NO
An unforgivable mistake, occurs when writers slip commas between subjects and verbs.

I do hope that the misplaced comma in the previous sentence caught your eye. If you’re a grammar curmudgeon, you should have been composing your letter to the editor before you reached the end of the sentence.

The mistake becomes less obvious the farther the subject is from its verb. Often the problem is that the sentence is too long. We need a breath, so we insert a comma. Instead of pushing commas around, try keeping the subject and verb closer together. If you have to move extra stuff to another sentence, so be it.

Incorrect: The many motions filed over the years that the case was pending, unnecessarily drove up the costs of litigation.

The sentence above works just fine without the comma. A small alteration works well, too: "Many motions were filed over the years that the case was pending, unnecessarily driving up the costs of litigation."

Join Sentences – NO
A mere comma cannot join two complete sentences. At least not without help. The technical term for the unaided comma joining two sentences is a "comma splice." To most of us, it just feels like a run-on sentence.

Incorrect: The statute of limitations began to run two years earlier when the patient first suspected her doctor had made a mistake, her claim was dismissed.

The comma needs some help, which is available from the following words: for, and, nor, but, or, yet, so. Grammar students for years learned the list through the mnemonic "fanboys."

Correct: The statute of limitations began to run two years earlier when the patient first suspected her doctor had made a mistake, so her claim was dismissed.

If none of the fanboys suits your sentences and you still want to join them together, use a semi-colon.

Alternative: The statute of limitations began to run two years earlier when the patient first suspected her doctor had made a mistake; her claim was dismissed.

Note that if you want to fancy-up the link between two sentences connected by a semi-colon, you’ll need a conjunctive adverb followed by a comma. Don’t be scared by the term "conjunctive adverb"; I used it to get your attention.

Conjunctive adverbs include frequently used transition words like however, nevertheless, moreover, therefore and thus. Many writers innocently treat conjunctive adverbs like their little conjunction cousins (the fanboys listed above). This innocent mistake results in many run-on sentences. Remember that you can use a fanboy with just a comma; conjunctive adverbs need both a semi-colon and a comma.

Example: The statute of limitations began to run two years earlier when the patient first suspected her doctor had made a mistake; thus, her claim was dismissed.

When in doubt…
As a parting thought, many writers are ill served by the jingle "When in doubt, leave it out." Many other writers are equally ill served by the instruction "Add a comma whenever you pause."

Those tidbits of grammatical wisdom worked well when we spent evenings sitting by the fire reading great works of literature. We all developed an inner ear for grammar, and we mostly developed a common ear. We all knew how fine English sounded. Now that we don’t have time to sit around and read, we have to pay attention to grammar rules.

ABOUT THE AUTHOR
Suzanne E. Rowe is an associate professor at the University of Oregon School of Law, where she directs the Legal Research and Writing Program. She is grateful to Amy Nuetzman of Oregon’s Academic Learning Services for comments on this article.

© 2007 Suzanne E. Rowe

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