When & How to Use an Em Dash

Instructor: Ian Matthews

Ian teaches college writing and has a Master's in Writing and Publishing

In the age of texting, it almost seems outdated. But this scrappy little line is versatile enough to sub in for parentheses, commas, semicolons, and more - let's take a look at some use cases for your new favorite punctuation mark: the em dash.

Why Use an Em Dash?

Unlike some other punctuation marks, there's no case where you have to use an em dash. There are some times, though, when the em dash makes more sense for the sentence you're writing. Since it usually signals a pause in the flow of the sentence, the em dash can be used instead of many other punctuation marks - it all depends on the kind of pause you want to suggest to your reader. See what I did there? Let's take a look at some times when an em dash may be beneficial to your writing.

Parentheses

Parenthetical statements (like this one) are usually used by writers to sneak in some additional information to the sentence without making the sentence structure too complicated. If you wanted to, you could skip over the information in those and not miss much. Think of parentheticals as the author whispering under her breath to you.

When a pair of em dashes replaces a pair of parentheses - like these are - that info is harder to ignore. The writer is drawing the reader's attention to the info there, since it's more separate visually. Consider the difference here:

  • Sheila fed her cats (all 38 of them) every morning before making a pot of coffee.
  • Sheila fed her cats - all 38 of them - every morning before making a pot of coffee.

It's a subtle shift, but even though the words in the sentences are the exact same, changing from parentheses to dashes changes the tone of the sentence as well. One thing to note here: if you're replacing parentheses at the end of a sentence, you'll only use one em dash. Here's that sentence one more time with that in mind:

  • Every morning before she made a pot of coffee, Sheila fed her cats - all 38 of them.

Commas

Just like they can with parentheses, pairs of em dashes can also replace pairs of commas. The end result looks pretty much the same, too. Take a look at this sentence:

  • I picked up my brother Jerry, a spaceship mechanic and a real jerk, at the airport.

That phrase between the commas, 'a spaceship mechanic and a real jerk,' is called an appositive phrase: it renames Jerry. If you took it out, the sentence would still work just fine. Here's the same sentence with em dashes in place of the commas:

  • I picked up my brother Jerry - a spaceship mechanic and a real jerk - at the airport.

Again, similar to with parentheses, the em dashes are more attention-grabbing and in-your-face than the punctuation they're replacing.

Colons & Semicolons

Em dashes can also be used instead of both colons and semicolons. A colon is most often used to start a list, like so:

  • We offer three cooking classes at the Institute: Japanese, Italian, and French.

The em dash just fits in the same spot as the colon:

  • We offer three cooking classes at the Institute - Japanese, Italian, and French.

The semicolon is used when a writer wants to join two independent clauses, two complete sentences, into one sentence:

  • We started the Japanese course a few years ago; it's been our most popular course ever since.

Here again, the em dash makes an easy replacement:

  • We started the Japanese course a few years ago - it's been our most popular course ever since.

Like with all of these other punctuation marks, the em dash is a less stuffy, more informal way to get the same pause in sentence flow across.

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