A lot of people mistakenly believe that using dashes is "bad grammar." However, they are perfectly acceptable forms of punctuation that can be used in place of other punctuation marks such as commas, semicolons, parentheses, and colons. The following guide should help you understand how dashes change sentences and when they are best utilized. This guide assumes that you already have an understanding of how to use these other forms of punctuation.
Punctuation marks are all simply visual representations of pauses. Choosing to use dashes in the place of these other forms of punctuation is a stylistic choice, with the dash conveying a different type of pause than commas, semicolons, parentheses, or colons. As Strunk and White explain, a dash is "stronger than a comma, less formal than a colon, and more relaxed than parentheses" (9). Because they are "stronger," dashes tend to, as The Holt Handbook explains, "call attention to the material they set off" (611). Whether you choose to use dashes or one of the other types of punctuation marks depends upon how you want the reader to perceive the information you are setting off -- most readers tend to pay more attention to what comes after or in between the dashes, while they may tend to pay less attention to what falls inside commas and parentheses and after colons and semicolons.
Dashes should not be overused. Part of the reason that readers pay more attention when a writer uses the dash is because it is not as common as the other forms of punctuation. If you are using dashes to draw attention to important points, but there are dashes drawing attention to important points in almost every sentence, then none of those points is especially standing out from the others. While The New Century Handbook recommends using "one pair per sentence at most" (882), this, even seems a bit generous. Think of it this way: when you're telling a story to your friends, if you are overly loud or overly animated through most of the story, they won't know which parts are the important parts, but if you save the volume and animation for a few very specific parts, they are understanding the point of your story closer to the way you want them to. Use the style and animation that the dash allows you sparingly, and it will garner you much better results. As Strunk and White recommend, "use a dash only when a more common mark of punctuation seems inadequate" (9).
Now that you've been warned about overusing dashes, what follows is a guide to the typical uses of the dash. All of the example sentences below are taken from several published reviews of the movie The Grudge so that you can see how dashes are being used by several different authors, though for the same purpose and with about equivalent levels of formality. Use these links to jump to specific information you are looking for --
[parenthetical statements & appositives] [series] [other nonessential material] [interruption]
-- or go through all of the categories in order.
Dashes can be used to set off nonessential material in a sentence that you could otherwise set off with either parentheses or commas. The difference is that dashes draw attention to the information they set off rather than making it seem, well, nonessential (New Century 881, Holt 611, Little, Brown 196). If punctuation marks indicated different types of pauses that would be present if the sentence were spoken aloud, imagine that dashes are a dramatic pause, and that the information within them would be spoken in a more animated or forceful way.
Read the sentence below as it is punctuated with the parentheses. Then move the cursor over the sentence to see how it would be punctuated with dashes.
Glieberman, Owen. "The Grudge." Entertainment Weekly. 20 Oct 2004. 27 Oct 2004. http://www.ew.com/ew/article/review/movie/0,6115,726330_1_0_,00.html.
The above sentence is a great example of the difference between using parentheses and dashes. The parenthetical statement is about emphasis, but by putting it inside parentheses, the author would have been doing the exact opposite of emphasizing the statement. In this case, using dashes was a more accurate representation of the author's intentions.
The following three sentences are also examples of using dashes to set off information that would otherwise be set off by parentheses or commas, and in turn emphasizing rather than deemphasizing that information. Take a look at how the sentence works with both types of punctuation. Does the meaning of the sentence change much based on which punctuation the author chooses?
Covert, Colin. "Movie review: 'The Grudge' is subtle horror." Minneapolis Star Tribune. 22 Oct 2004. 27 Oct 2004. http://www.startribune.com/stories/412/5042452.html.
Denerstein, Robert. "'Grudge' all atmosphere." Rocky Mountatin News. 21 Oct 2004. 27 Oct 2004. http://www.rockymountainnews.com/drmn/movies/article/0,1299,DRMN_23_3271611,00.html.
Havis, Richard James. "The Grudge." The Hollywood Reporter. 22 Oct 2004. 27 Oct 2004. http://www.hollywoodreporter.com/thr/reviews/review_display.jsp?vnu_content_id=1000682249.
A lot of people, and visual-spatial learners and speed-readers especially, will tend to skip over information that is set off by commas or parentheses because those punctuation marks indicate to them that it is not essential to understanding the sentence. By choosing dashes in the above examples, the authors are making sure that the reader will not only read but pay extra attention to the information the dashes set off.
Dashes can also be helpful in the instance that you have a longer piece of nonessential information to include in the sentence. Dashes, in this case, can act as a visual cue to help the reader recognize where the nonessential information begins and ends so that they have a stronger sense of the flow of the main part of the sentence. In the example below, the nonessential information is not especially long, but long enough that the visual cue the dashes provide helps the reader keep up with the main idea of the sentence while it still gives helpful background information that makes the sentence more meaningful.
Havis, Richard James. "The Grudge." The Hollywood Reporter. 22 Oct 2004. 27 Oct 2004. http://www.hollywoodreporter.com/thr/reviews/review_display.jsp?vnu_content_id=1000682249.
It may take a little bit of extra effort at first to pause when setting off nonessential information and ask yourself what punctuation mark best reflects how you wish the reader to perceive the nonessential information, but after a little bit of practice, you should know when to use dashes and when to stick with the parentheses or commas. Dashes should be used sparingly, however - they won't have as much power if they are used too frequently.
Generally, dashes can be used in series for three reasons. The first involves using dashes to set off a series in its entirety. Often they are used to instert the series into the middle of a sentence (New Century 881, Holt 611, Little, Brown 196). Like the above examples, this could otherwise be punctuated with parentheses, but also like the above examples, the choice of dashes over parentheses calls attention to the series rather than marking it in the mind of the reader as less important. Here are two examples of dashes being used for this purpose:
Hartlaub, Peter. "Mindless killing weakens 'Grudge.'" The San Francisco Chronicle. 22 Oct 2004. 27 Oct 2004. http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/10/22/DDGRH9D43P1.DTL.
Hunter, Stephen. "'The Grudge': Horror That Translates Chillingly." The Washington Post. 22 Oct 2004. 27 Oct 2004. http://www.washingtonpost.com/wp-dyn/articles/A53131-2004Oct21.html.
In both cases, this choice by the author makes the series the visual, and ultimately semantic, focal point of the sentence. The series does not have to be in the middle of a sentence in order for dashes to be used. A dash could be used after the introduction of a series in place of a colon, as demonstrated in a rearrangement of the previous example:
A dash can also follow a series to indicate a summation of that series, this time emphasizing what you as author wish the reader to see as the significance of the series, also illustrated in a rearrangement of the last example:
Dashes can also be used to bring attention to specific items in a series. In both of the following sentences, the author uses a dash instead of a comma to set off the last item in the series in order to make sure the reader knows that it is the most important or interesting item in that series:
Ebert, Roger. "The Grudge." The Chicago Sun-Times. 22 Oct 2004. 27 Oct 2004. http://rogerebert.suntimes.com/apps/pbcs.dll/article?AID=/20041021/REVIEWS/40922015/1023_)
Hartlaub, Peter. "Mindless killing weakens 'Grudge.'" The San Francisco Chronicle. 22 Oct 2004. 27 Oct 2004. http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/10/22/DDGRH9D43P1.DTL.
If you are having trouble placing a series in a sentence or want the reader to take special notice of a specific item in your series, dashes are a good way to accomplish this.
Dashes can also be used in place of colons and semicolons, indicating complete-sentence-length nonessential information, qualifying statements, and explanations (New Century 881, Holt 379, Little, Brown 196). Observe the two punctuation options for the following sentence:
Covert, Colin. "Movie review: 'The Grudge' is subtle horror." Minneapolis Star Tribune. 22 Oct 2004. 27 Oct 2004. http://www.startribune.com/stories/412/5042452.html.
In the above sentence, the information following the punctuation mark is explaining what the author means by "telegraphic and puzzling." The colon is a more formal choice of punctuation, but using it, especially when it is followed by what seems like a lot of information, may make the sentence more daunting for the reader than you intend. The dash, for lack of a better description, makes the sentence a little more friendly-looking. Either choice is correct, but one may be better for your intended audience than the other. The following sentence is a similar case:
Clark, Mike. "The Grudge." USA Today.. 21 Oct 2004. 27 Oct 2004. http://www.usatoday.com/life/movies/reviews/2004-10-21-grudge_x.htm.
Once again, either the colon or the dash is correct, and should be chosen based on the tone you are trying to create as the writer. The tendency of the reader is to pay more attention to what follows the dash, so choosing to use the dash makes the second part of the sentence seem the more important part, while the colon makes them appear more equal or makes the first part seem the more important.
The dash can also be used in place of the semicolon (in between two closely-related independent clauses):
Hartlaub, Peter. "Mindless killing weakens 'Grudge.'" The San Francisco Chronicle. 22 Oct 2004. 27 Oct 2004. http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/10/22/DDGRH9D43P1.DTL.
Both the semicolon and the dash are correct ways of punctuating this sentence, but just as with all the other examples here, choosing to use the dash means drawing additional attention to what follows the dash and making this the important part of the sentence. Your choice as the writer will depend upon what you want the reader to pay more attention to. The above authors chose the dash because they wanted their readers to pay more attention to the second parts of these sentences.
Finally, there is one thing that dashes can do that other punctuation marks cannot, and that is to indicate interruption (Holt 611). The closest you can get to conveying this with another punctuation mark is to use elipses (...), but these indicate trailing off rather than abrupt interruption. This example illustrates how a dash can be used for this purpose:
Ebert, Roger. "The Grudge." The Chicago Sun-Times. 22 Oct 2004. 27 Oct 2004. http://rogerebert.suntimes.com/apps/pbcs.dll/article?AID=/20041021/REVIEWS/40922015/1023_)
The dash here is still drawing attention to what follows it, but at the same time helps bring out the voice of the author. As an occasional stylistic device, using a dash to interrupt a line of thought can go far in helping you write with a distinctive and interresting voice.
Kirszner, Laurie G. and Stephen R. Mandell. The Holt Handbook, 6th Ed. Orlando: Harcourt College Publishers, 2002.
Aaron, Jane E. The Little, Brown Compact Handbook, 3rd Ed. NY: Longman, 1998.
Hult, Christine A. and Thomas N. Huckin. The New Century Hanbook, 3rd Ed. NY: Pearson Longman, 2005.
Strunk, William, Jr. and E.B. White. The Elements of Style, 4th Ed. NY: Longman, 2000.