Grammar Time: Using Em Dashes

This week’s Grammar Time will discuss a frequently used but rarely discussed punctuation mark—the mighty em dash!

The em dash is a handy and versatile punctuation mark. In fact, em dashes can replace parentheses, colons, semicolons, and (sometimes) commas—but that doesn’t mean that they’re completely interchangeable with these other punctuation marks.

So how do you correctly use an em dash? As a general rule, em dashes imply more emphasis and are less formal than other punctuation options. Just take a look at the following examples:

She was watching a TV show (Friends) when he arrived.

She was watching a TV show, Friends, when he arrived.

She was watching a TV show—Friends—when he arrived.

In the first example, it’s not particularly important that she was watching Friends in particular. Using em dashes instead of parentheses, as in the third example, shows that it’s important that she was watching Friends instead of any other show. The middle example, using commas, is somewhere in between—it neither emphasizes nor deemphasizes Friends.

As a bonus tip, if you use em dashes to offset a parenthetical, you need an em dash on both sides of the phrase. It not only looks cleaner but it helps the reader follow the sentence.

Concerning emphasis and de-emphasis, the same rule is true when an em dash replaces a colon or semicolon. Compare these sentence pairs:

I have two pets: a dog and a cat.

I have two pets—a fox and an owl.

I can’t go to the party; I have a test the next day.

I can’t go to the party—I have a test the next day.

For the first pair of sentences, the em dash is used in the second example because a fox and an owl are very unusual pets; it makes sense to emphasize this by using an em dash instead of a colon. In contrast, it’s fairly common to have dogs and cats as pets, so the extra emphasis an em dash would provide isn’t necessary in the first example.

Similarly, using an em dash instead of a semicolon in the second set of examples puts more emphasis on the following information. The em dash makes it clear that the test is why the speaker can’t go to the party—otherwise, they’d be there in a heartbeat!

It’s very easy to use the em dash too much. Always ask yourself if you want to emphasize information or not, and try to limit em dashes to once or twice a paragraph. Also keep in mind that em dashes are less formal, so they might not be appropriate in more formal writing, like cover letters and other professional documents.

If you keep these tips in mind, you’ll be using em dashes like a pro.