So you know how to use commas, apostrophes, quotation and exclamation marks. Let’s talk about some graduate level punctuation — the em dash.
You’re probably seen this guy before. It basically looks an extended hyphen, and it’s named em dash because it takes up the same amount of room as a capital letter M.
More useful than a hyphen, this dash is the workhorse of your punctuation toolkit. You can use the em dash to replace commas, parentheses, or colons, but the meaning changes slightly in each situation.
Using a pair of em dashes to replace commas in a sentence can help improve readability; however, the effect will be more forceful.
When Julie turned in her term paper—two weeks after the due date—her professor told her she would automatically receive two letter grades off her final grade.
A pair of em dashes can also replace a pair of parentheses. When writing, consider the point you are trying to make. Dashes are less formal, but they also make the content stand out. Use dashes to call attention to the material and parentheses to be more subtle. Other punctuation that would be used with parentheses, like commas, should be removed.
Julie had a lot of excuses for her professor (five emails worth), but he wouldn’t budge on the grade.
Julie had a lot of excuses for her professor—five emails worth—but he wouldn’t budge on the grade.
When the em dash is used in place of parentheses at the end of a sentence, only a single dash should be used.
Julie finally accepted the grade she deserved (but knew she would have to make it up on the final exam).
Julie finally accepted the grade she deserved—but knew she would have to make it up on the final exam.
Use an em dash at the end of your sentence as a way to emphasize the conclusion in an informal manner.
Julie made sure to attend every study session offered by the professor and was rewarded with her ultimate goal—a passing grade.
This punctuation mark is really only coming to play in written text—you’re probably not speaking the em dash. Modern word processors make it easy, and most will create the em dash when you type a pair of hyphens. It’s also up to you whether you want to insert spaces around the em dash. AP style — which is followed by most news organizations — will insert a space before and after the em dash. If you choose not to—or your organization has its own style guide—that’s perfectly correct as well.