Module 14, Additional Punctuation, Lesson 5:

The Em Dash and En Dash


Note: If you've already completed Lesson 4, the very beginning of this lesson will be review.

The Three Punctuation Marks in the Hyphen and Dash Family
The hyphen -
The en dash
(the width of a capital N, twice the width of a hyphen)
The em dash
(the width of a capital M, three times the width of a hyphen)

In the past, each of these marks was much easier to distinguish on a typewriter than on today's computers. Modern computers generally change two hyphens with no spaces before, after, or between them to an em dash. Different operating systems and word programs have different ways of typing these marks.

Definition: The em dash (sometimes just called a dash) is used to set off information from the rest of the sentence, and mimics or copycats other more formal punctuation marks. It is often used in place of colons or semicolons. It is also common to use a pair of em dashes to replace parentheses or a pair of commas. Using the em dash (or a pair of em dashes) to replace other marks is not always appropriate. In formal writing, avoid using dashes unless they are really necessary. The em dash is more dramatic than traditional punctuation but also more informal. Using em dashes can be an excellent way to add emphasis to an idea (continue reading for more information). Remember not to overuse dashes: doing so can cause confusion or make your writing sound choppy.

In American style it is not necessary to put a space on either side of the em dash, but British style does require a space on either side. This lesson adheres to American style.

In Place of Parentheses

Use an em dash to set off parenthetical ideas that you want to emphasize.

Mr. Nelson (who lives next door to me) is our new teacher.
Mr. Nelson—who lives next door to me—is our new teacher.

In Place of Commas

  • Parenthetical ideas can be set off by commas, but it can be helpful to use em dashes for emphasis.
    My entire trip, from the delayed takeoff to the bumpy landing, was an experience I would rather forget.
    My entire trip—from the delayed takeoff to the bumpy landing—was an experience I would rather forget.
  • Use a pair of em dashes to set off an appositive that contains commas. Appositives are normally set off with commas, but when there are commas within the appositive itself, using em dashes instead helps avoid confusion.
    Caroline keeps a list of her food allergies, peanuts, shellfish, and soy, taped to her EpiPen in case of emergencies.
    Caroline keeps a list of her food allergies—peanuts, shellfish, and soy—taped to her EpiPen in case of emergencies.

In Place of a Colon

  • Use an em dash to signal the start of a list. This is less formal than a colon and also more dramatic.
    Jeremy has three big guard dogs: Kitten, Bunny, and Mouse.
    Jeremy has three big guard dogs—Kitten, Bunny, and Mouse.
  • Use an em dash to signal a restatement or contradiction.
    After all my hard work, I received a B on the final—I had passed the class.
    I was surprised that all the students remembered to bring their homework—all 24 of them.
    I had originally decided to see the horror movie—but I saw the romantic comedy instead.

In Dialogue

Use an em dash in place of an ellipsis when someone is interrupted abruptly.

ENRIQUE: Then we went to see a castle on the—
SIENNA: Watch out! You almost ran into that pole.

When using quotation marks for the interrupted dialogue, the em dash goes inside.

"Then we went to see a castle on the—"
"Watch out! You almost ran into that pole."

A note about the en dash: Because the en dash is starting to be used less frequently, this lesson will not cover it in depth. It is still used to denote number ranges (please read pp. 26–64; The meeting will be from 3:00–4:00) and in some hyphenated compounds and two-word open compounds. If you would like to learn more about how to use the en dash, please refer to the Chicago Manual of Style or the Associated Press Stylebook.

Practice What You've Learned

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Insert one or more em dashes in each of the following sentences by clicking the space(s) between the appropriate words.