Using the comma for rhetorical effect (p. 465)

1. Jill jumped up and down when she heard the news.

Can you hear a slightly different shade of meaning in the following sentence?

2. Jill jumped up and down, when she heard the news.

And what about,

3. When she heard the news Jill jumped up and down.

Or,

4. When she heard the news, Jill jumped up and down.

The differences are in emphasis, created by the pauses that the commas force the reader to make. Grammatically, a comma is not necessary in the first pair of sentences, but is in the second. Some readers might even consider sentences 2 and 3 to break a rule.

As you become familiar with the standard rules of comma use (see The Brief New Century Handbook, Second Edition, pages 435-442), you can understand how intentionally breaking a rule could create a very special effect. In fact, it's widely held among professional writers that the best writing sometimes intentionally breaks rules for impact--though you can't "intentionally" break a rule you don't know to begin with.

Commas produce pauses for a reader, and pauses create emphasis. Whatever words come immediately before and after a pause receive emphasis that they would not receive without it (see Website Supplement 32.2). By adding or removing commas, then, you can increase or decrease the emphasis a particular word receives. (Just be certain that adjusting the commas doesn't destroy the sense of the sentence.)

You might, for instance, elect not to use a comma before a coordinating conjunction to separate independent clauses:

5. It was late at night and Jim's headache was intense.

The effect is one of more closely connecting (by removing the pause and emphasis from between) the two independent clauses in that sentence.

You might also elect to add a comma where one is not necessarily needed:

6. Today, I'm doing the laundry.

The comma creates emphasis on today or I'm. Without it, most of the emphasis would be placed on laundry. How is the emphasis of sentence 7 changed by adding a comma?

7. The young pianist continued to hammer away badly.
8. The young pianist continued to hammer away, badly.

Handbooks don't include rules for deciding how to manipulate punctuation for your rhetorical purposes. Instead, you have to ask yourself what meaning you want to convey, and make sure that your punctuation conveys that meaning.