A dash is a little horizontal line that floats in the middle of a line of text (not at the bottom: that’s an underscore). It’s longer than a hyphen and is commonly used to indicate a range or a pause. Dashes are used to separate groups of words, not to separate parts of words like a hyphen does. There are three forms of dashes: em, en, and the double hyphen.

The most common types of dashes are the en dash (–) and the em dash (—). A good way to remember the difference between these two dashes is to visualize the en dash as the length of the letter N and the em dash as the length of the letter M. These dashes not only differ in length; they also serve different functions within a sentence.

Em Dashes

Using the Em Dash to Set Off Parenthetical Information

Em dashes are often used to offset parenthetical information—that is, information you might put in parentheses. When you use parentheses, though, the emphasis is taken off the parenthetical information and put on the rest of the sentence. When you use em dashes, on the other hand, the emphasis is put on the information within the dashes.

For this usage, make sure there are two em dashes: one on each side of the parenthetical information. Using spaces before and after an em dash is a matter of preference; just be consistent. Consider the examples below for reference:

While I was shopping—wandering aimlessly up and down the aisles, actually—I ran into our old neighbor.
An etymological dictionary is one of the few books—no, it’s the only book—you’ll ever need.
There has recently been an increase—though opposed fiercely by many people—in alternative education practices.
He was going to call off the project—or was he?—when the client increased the payment.
Traveling—that is, traveling by public transit—can be a relaxing activity if you bring music and reading material along with you.

Using the Em Dash to Set Off Appositives that Contain Commas

An appositive is a small section of extra information that is inserted into a sentence for clarification. Commas are usually used to offset the appositive, but if the appositive contains one or more commas, adding additional commas would be confusing for the reader. When using an appositive that contains a comma, offset it with dashes, instead.

Four of us—Mike, Amanda, Katy and me—went to the conference last week.
Mr. M. glanced surreptitiously at his watch—his gold, diamond-encrusted watch—and suggested the meeting might adjourn for the day.
If you need something, call my assistant—Catherine, not Margaret—and she’ll help you.
Materialism—always wanting something more, something different—is good for the economy but bad for the soul.
The question words—who, what, when, where, why, and how—are used to retrieve information in English.

Using the Em Dash to Bring Focus to a List

When a sentence begins with an independent clause and ends with a list, you can use a colon between the clause and the list. When the list comes first, it’s better to use a dash to connect the list to the clause. This helps to take three potentially random things and focus them toward one idea, which is easier for the reader to process.

Dishes, laundry, dusting—they’re all done now, and I need a rest.
Crocodiles, alligators—they both look the same to me and they look equally dangerous!
Chocolate, strawberry, vanilla—all ice cream tastes good, especially on a hot summer’s day.
Do this, do that, go here, go there—there’s so much to do that I don’t actually get much accomplished during the day.

Using the Em Dash to Mark Sharp Turns in Thought

Dashes can act like little warnings (like yellow road signs) that whatever the writer has been doing is about to change. Dashes identify a sudden break in the sentence as the writer changes tack, perhaps going in another direction entirely, or perhaps just pausing to insert another thought. This effect is usually fairly informal, and isn’t recommended for academic writing (it might look like you don’t know what you’re talking about). Consider the examples below:

Mary, could you—no, Mikey, don’t touch the sharp knife!—Mary, could you please set the table?
Dinner is at 6:30—not 6:29 or 6:31.
Where the heck is my—wait, what was I looking for?
Would you please—oh, never mind…

En Dashes

Recall that en dashes are slightly shorter in length than em dashes. En dashes may look similar to em dashes, but they function in a much different way.

Using the En Dash to Indicate Spans of Time or Ranges of Numbers

The en dash is often used to indicate spans of time or ranges of numbers. In this context, the dash should be interpreted as meaning either “to” or “through.” Consider the examples below:

The teacher assigned pages 101-181 for tonight’s reading material.
The scheduled window for the cable installation is 1:00–3:00pm.
The 2015-2016 fiscal year was the most profitable year for the new business.

Using the En Dash to Denote a Connection

The en dash may also be used to indicate a connection between two words. Use an en dash when you need to connect terms that are already hyphenated or when you are using a two-word phrase as a modifier. When the dash is used in this way, it creates a compound adjective. See the following examples:

The pro-choice–pro-life argument is always a heated one.
The Nobel Prize–winning author will be reading from her book at the library tonight.

Weekly Grammar Tips
Weekly Grammar Tips
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