Our Friend, the Comma

A period tells the reader to come to a full stop. A comma tells the reader to pause, and then continue the natural flow of the sentence. The "sound" of the sentence should offer some guidance for the placement of commas, but there are also some standard conventions which ought to be followed. The following examples show the six primary uses for a comma.

1. Put a comma should precede a coordinating conjunction (and, or, but, nor, for) when the conjunction joins two independent clauses. In other words, if you have two related statements, each with its own idea, you can separate them with a comma.

I'd like to buy some jumbo shrimp, but I don't understand how they can be jumbos and still be shrimps.

The second statement, a comment about the first statement, is introduced by "but" so the comma is used to tell the reader to pause.

2. A comma should follow introductory clauses and phrases. Here's an example from a Mercedes-Benz ad:

Technologically speaking it had no rivals . . . Even standing still the S 320 leaves other cars behind.

"TechnologicallY and "Even standing still" are introductory phrases which require some kind of punctuation to set them off from the main idea of the sentence.

Here's another example from a Ford Citibank ad:

To apply see your Ford or Lincoln-Mercury dealer.

"To apply" is an introductory phrase. The rest of the sentence could stand alone without it. Look at this next statement and notice that the words "To apply" do not introduce the sentence.

To apply is to be rejected.

3. A comma should follow transitional words (like furthermore and therefore) that introduce sentences.

This dealer offers low prices. Furthermore, he backs his merchandise with a 12-month guaranty.

4. Use commas to separate items in a series.

Their house is filled with books, plants, pets, and children.

NOTE: There's an important difference between the comma and the colon when presenting a list. If you're not sure about it, read the file on colons.

5. Use commas to set off nonrestrictive (non-essential) information. Look at the following example from a Coca Cola ad.

The Coca Cola Company in collaboration with Franklin Heirloom Dolls, authorizes their first ever heirloom collector doll.

The phrase "in collaboration with Franklin Heirloom Dolls," should be set off by commas, and there is one after Dolls; however, the phrase needs a balancing comma after the word Company.

Actually, you could get away with no commas at all in this sentence, but having put in one, you MUST include the other.

Another way to make decisions about commas is to read your sentence aloud. Try it with this next example.

She is, I believe, the best candidate.

Notice how the pitch of your voice drops when you speak the part that's set off by commas?

6. Use commas in geographical names and in dates, as in

Austin, Texas

July 4, 1776

[See the file on comma splices to learn more about this subject.]

7. CBS television committed a comma error in their ads for Scarlett, the sequel to Margaret Mitchell's "Gone with the Wind." Attempting to quote a famous line from the original film, the ad stated:

Frankly my dear, I don't give a damn.

The sound track for the ad said "It was the most controversial statement of its time." The screenplay had it this way:

Frankly, my dear, I don't give a damn!

Notice the comma after "Frankly" and the exclamation point at the end.

Here's how it appeared in the original novel:

He drew a short breath and said lightly but softly:

"My dear, I don't give a damn."

The rule is pretty simple. In statements like this (a direct address), the name or its substitute (in this case, "my dear" is a substitute for the name) must be set off by commas. The same holds true for Sherlock Holmes's famous statement:

Elementary, my dear Watson.

(By the way, it never appeared in the Sherlock Holmes novels by Arthur Conan Doyle. Basil Rathbone introduced it in the movies.)

Here's another example of comma errors in public documents. This line is from an ad by Toyota:

To us, a successful business shouldn't just try to make a profit, it should try to make a difference as well.

There are actually two sentences here. This error is called a comma splice. Two complete sentences are joined by a comma. A semi-colon after "profit" or a period after that word, followed by a new sentence, would have fixed it, as shown below:

To us, a successful business shouldn't just try to make a profit; it should try to make a difference as well.

or

To us, a successful business shouldn't just try to make a profit. It should try to make a difference as well.