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Commas, parentheses, and em dashes

by Ms. Grammar

We often include information in a sentence that needs to be set apart in some way. Typically, commas, parentheses, or em dashes are used. But which should it be? For example, in the following sentence, would you use a pair of commas, parentheses, or em dashes?

The power plug condition___whether it is too loose or too tight in the outlet___can cause several problems.

In this column:
Guidelines
More information
Writing for the Web?
Test Yourself

Guidelines

According to The Great Grammar Challenge, the answer depends on the intent of the sentence, and in many cases, you can justify whatever you choose.  Great Grammar suggests the following guidelines, which are easy to remember and can help you apply treatments consistently. Of course, if your company has a style guide covering the use of these punctuation marks, you will need to follow the style guide.

»    Use em dashes to emphasize information, or to set off a series that already includes commas.
Em dashes tell the reader: Read this information—it’s important!

»    In general writing, use parentheses to deemphasize information.
Parentheses tell the reader: Skip this information if desired; it’s not that important.

»    In technical writing, use parentheses for information that elaborates on or clarifies the sentence.
Parentheses tell the reader: Here is more information about this topic.

»    Use commas for information that goes with the flow of the sentence. Commas tell the reader: This information is as important as anything in the sentence.

Using these guidelines, the correct choice for the example above would seem to be to use either commas (goes with the flow) or parentheses (more information), depending on the writer’s intent.

More information

As you would expect, The Chicago Manual of Style has much more to offer on these punctuation marks.

Regarding the resource for this article, Ms. Grammar has mentioned The Great Grammar Challenge before. Written by Priscilla S. Taylor and Mary Stoughton and published by EEI Press (1997), Great Grammar lives up to its name. Look for it on the EEI Communications site. 

Writing for the Web?

If you are preparing content for the Web, read Peter Sheerin’s discussion on correct codes for  special characters, The Trouble with EM ‘n EN (and Other Shady Characters). Although written quite a while ago, Sheerin’s article is packed with information.

Test Yourself

In the following sentences, choose em dashes, commas, or parentheses to set off the information.

1. Only two types of user___Engineer or Administrator___can access the system.
2. After the first day of the conference ___December 4th___ the venue was changed due to the storm damage at the Convention Center.
3. The diagram shows the five customer support stages___not including the initial  customer inquiry___and identifies the employee responsible at each stage.
4. Hillary Brown___who worked at IBM before joining GoDaddy___has been promoted to Vice President.
5. The start parameters___the original selections made in the Define Project dialog box ___ are deleted from the database after the project is run and saved.
6. The warning message___which flashes red in the status bar___must be acknowledged before the process will continue.

Answers

Ms. Grammar’s selections are as follows, with the reasons listed after the sentences. See if you agree.

1. Only two types of user—Engineer or Administrator—can log on to the main system. Important information the user needs to know.
2. After the first day of the conference  (December 4th) the venue was changed due to the storm damage at the Convention Center. Take your pick: it either elaborates on the sentence or is information that can be skipped.
3. The diagram shows the five customer support tasks (not including the initial  customer inquiry) and identifies the employee responsible for each task. Clarifies the information.
4. Hillary Brown, who worked at IBM before joining GoDaddy, has been promoted to Vice President. Goes with the flow.
5. The start parameters (the original selections made in the Define Project dialog box) are deleted from the database after the project is run and saved. Clarifies the information.
6. The warning message—which flashes at the bottom of the screen—must be acknowledged before the process will continue. Important information the user needs to know.

This entry was posted on Monday, February 9th, 2009 at 6:00 am and is filed under January/February 2009 Issue, Rough Draft Newsletter. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

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