The em dash is one of the most versatile punctuation marks. Depending on the context, it can replace commas, parentheses, or colons, each time producing a slightly different effect.
While the em dash is highly useful, it’s best to limit its use to two appearances per sentence to avoid confusion. Do not confuse the em dash (—) with the slightly narrower en dash (–) or the even narrower hyphen (-); these marks serve different purposes, which are discussed in other sections.
1. Em Dashes in Place of Commas
A pair of em dashes can be used instead of commas to enhance readability. However, dashes are more emphatic than commas.
Example:
- The puppy—the one with the floppy ears and wagging tail—charmed everyone at the park.
2. Em Dashes in Place of Parentheses
Em dashes can replace parentheses. Dashes are less formal and more intrusive, making them suitable for drawing attention to the enclosed content.
Examples:
- The results of the experiment (which were unexpected) were published in a leading journal.
- The results of the experiment—unexpected and groundbreaking—were published in a leading journal.
Note: When used at the end of a sentence, only a single em dash is needed.
Example:
- She decided to move to London (after much deliberation).
- She decided to move to London—after much deliberation.
3. Em Dash in Place of a Colon
The em dash can also replace a colon when emphasizing the conclusion of a sentence. The dash is less formal than a colon.
Examples:
- The team was finally ready for the big game—everything was in place.
- He had one goal for the day—finish the project before the deadline.
4. Multiple Em Dashes
Two em dashes can indicate missing portions of a word, whether unknown or intentionally omitted.
Examples:
- The witness, M. S—, stated that he had seen the incident.
- The documents were signed by the board members, M. B—, and J. H—, but not by the president.
When an entire word is missing, you can use either two or three em dashes consistently throughout your document. Surrounding punctuation follows standard placement rules.
Example:
- The suspect—who had no alibi—was arrested yesterday.
5. Spaces with the Em Dash
Typically, the em dash is used without spaces on either side, which is the style followed in this guide. However, most newspapers set the em dash off with a single space on each side.
Example:
- Most news articles—especially those that follow AP style—insert a space before and after the em dash.
6. Producing the Em Dash
Many word processors automatically convert a pair of hyphens into an em dash. If not, look for an “insert symbol” option in your software. On a typewriter, a pair of hyphens is the closest approximation to an em dash.