What is an em Dash?

What Is an Em Dash?

An em dash (—) is created in most word processing programs when the user types two hyphens. The hyphen keys are typically located next to the zero key on a computer keyboard.

How Is an Em Dash Used?

Em dashes have four distinct purposes. First, a pair of em dashes can replace a pair of commas.

This substitution should be used to emphasize the words enclosed in the em dashes. In the example below, notice the difference in emphasis when a em dashes replace the commas.

• When Susan finally received her final grades, months after the semester had ended, she realized the registrar had transposed the numbers in her zip code.
• When Susan finally received her final grades--months after the semester had ended--she realized the registrar had transposed the numbers in her zip code.

Em dashes can also replace parentheses within a sentence. Again, the em dashes will emphasize the parenthetical information. Look at the way Henry David Thoreau uses em dashes in the example below.

'I meet this American government, or its representative, the state government, directly, and face to face, once a year--no more--in the person of its tax gatherer.'

Em dashes can also serve as a substitute for a colon, as in the following example.

The movieplex is showing three classic Hitchcock movies--North by Northwest, The Man Who Knew Too Much, and Rear Window.

Finally, em dashes can be used to show interrupted thought or dialogue. The following sentence exemplifies this usage.

As the attorney finished his speech to the jury, he looked directly at each of the jurors. 'I think you'll agree, ladies and gentlemen of the jury, that the real thief is--' he paused for dramatic effect.

A Word of Caution

Avoid overusing the em dash. This versatile punctuation mark can be effective when used appropriately, but first check your writing to determine if some other mark of punctuation might be more appropriate.