Better Punctuation—Getting the Versatile Em Dash Right

Writers, editors, and proofreaders need to know the ins and outs of this sometimes-forgotten dash, which adds variety to your punctuation—something that is always welcome. It can replace pairs of commas, parentheses, colons, and semicolons; but when is it correct to use?

What is an em dash?

In my post on en-dashes, I noted that dashes were longer than hyphens. An en-dash is the length of a capital N in a font, and an em dash is—predictably—the length of a capital M. There’s also the double em dash, along with the triple em dash. Here’s what they all look like:

• ‐ hyphen
• – en-dash
• — em dash

The Chicago Manual of Style (CMOS) prefers no space before or after em dashes, while AP style prefers spaces before and after them. In the UK, the em dash is frequently substituted with a spaced en-dash.

• CMOS: It adds variety to your punctuation—something that is always welcome. (em dash)
• AP: It adds variety to your punctuation — something that is always welcome. (spaced em dash)
• UK: It adds variety to your punctuation – something that is always welcome. (spaced en dash)

Here I will refer to em dashes, and you can apply the same conventions to spaced en-dashes if your project’s style guide or style sheet calls for them instead.

What is the correct use for an em dash?

If you’re like me, you weren’t taught about dashes at school or in college English courses. But dashes are quite versatile punctuation marks and can add some extra oomph to a sentence. They are dramatic and especially appropriate for abrupt breaks in thought.

To set off complementary or exemplifying statements

We can use em dashes to set off parenthetical thoughts that complement an item in the main clause, or the whole clause. These additions, examples, and explanations are usually marked with commas (less emphatic) or parentheses (more emphatic). Notice that in the following sentences, the phrases marked off can be removed without affecting the meaning (or completeness) of the main clause (“Black Friday is the biggest shopping day of the year”):

• Black Friday—a day many people trample over others to buy things they don’t need—is the biggest shopping day of the year. Why not capitalize on it in your marketing? (em dashes)
• Black Friday, a day many people trample over others to buy things they don’t need, is the biggest shopping day of the year. Why not capitalize on it in your marketing? (commas)
• Black Friday (a day many people trample over others to buy things they don’t need) is the biggest shopping day of the year. Why not capitalize on it in your marketing? (parentheses)

Related to this, we may use em dashes before expressions like “for example,” “that is,” and “namely”:

• Sparse punctuation, subtle literary devices, and a purposeful bending of the rules are evident in thrillers by best-selling authors, for example, Lee Child and Michael Connelly. (comma)
• Sparse punctuation, subtle literary devices, and a purposeful bending of the rules are evident in thrillers by best-selling authors (for example, Lee Child and Michael Connelly). (parentheses)
• Sparse punctuation, subtle literary devices, and a purposeful bending of the rules are evident in thrillers by best-selling authors—for example, Lee Child and Michael Connelly. (em dash)

Notice the slight difference in reading, a briefer pause when punctuated with commas, and a more methodical, longer pause when marked with parentheses. Em dashes fall in the middle. This is also the case when the additional thought is at the end of a sentence:

• Lowering our prices to compete in that market segment would damage our brand image—something that we will not do. (em dash)
• Lowering our prices to compete in that market segment would damage our brand image (something that we will not do). (parentheses)

Be careful not to use em dashes in proximity to other em dashes. To avoid confusion, you can alternate with commas or parentheses:

• Black Friday—a day many people trample over others to buy things they don’t need—is the day after Thanksgiving (when we are thankful for what we have). [em dashes and parentheses]
• In polishing their style, many writers subscribe to the “Five Cs”—correctness (in language and facts), conciseness, clarity, coherence, and completeness. [an em dash and parentheses]

To introduce an element or series of elements illustrating or amplifying an idea

Specifying an element or listing multiple elements to illustrate or amplify an idea is the traditional role of the colon, but em dashes are also correct:

• If a writer is to produce much of a publishable standard, they will have to cultivate key personal qualities—perseverance, determination, commitment, organization, patience, resilience, and confidence. (em dash)
• If a writer is to produce much of a publishable standard, they will have to cultivate key personal qualities: perseverance, determination, commitment, organization, patience, resilience, and confidence. (colon)

Likewise, an em dash can connect a sentence with another independent, complementary one, just as a semicolon can:

• Teaching during an important World Cup match in a football-obsessed country is nearly impossible—students are constantly checking their phones. (em dash)
• Teaching during an important World Cup match in a football-obsessed country is nearly impossible; students are constantly checking their phones. (semicolon)

To indicate a break or interruption

An em dash or a pair of em dashes can signal interruptions in thought or speech:

Codes and shortcuts for writing em dashes

There is no key for the versatile em dash on your keyboard, but you can write in one these ways:

• In Windows: hold down the ALT key and type 0151 (this works if you have a number pad).

• In Microsoft Word:
  • Use the command “insert symbol” and then select the em dash, or
  • Use the keyboard shortcut: CONTROL + ALT + minus sign on the numeric keypad. (You can add your own customized Word shortcuts.)
  • Go to Options>Proofing>Auto Correct Options and establish .em to be automatically corrected as the em dash sign. This is my favorite method.
• In WordPress and HTML: write — manually into your code (WordPress has an option to edit a block in HTML).

For more contexts and Apple users, see “How to make dashes” (Wikipedia)

I hope that clears up the most common questions about em dashes in your writing and proofreading. Don’t forget that—like anything—if you overuse the em dash in your writing, it will lose its power. Editors take issue with an excessive number of these dramatic dashes.

See also: What’s an en-dash? Soon to come: posts on hyphens and compound words.