Dashes (– or —)

Dashes can be used to separate extra information or to mark a break in a sentence. They appear in some of the same places as commas, colons, semicolons, and parentheses. However, they are generally considered more informal than these punctuation marks, so should be used sparingly and selectively in academic writing.

The two main types of dashes are the em dash (—) and the en dash (–). Make sure not to confuse dashes and hyphens (-).

Using dashes

Dashes can be used in pairs to mark off additional information or an aside that is not essential to the understanding of the rest of the sentence. Here they function similarly to parentheses or a pair of commas.

Dark, leafy greens—such as spinach, kale, and chard—are an important part of a healthy diet.
Some years ago—never mind how long precisely—I thought I would sail about a little and see the watery part of the world.

A dash can also be used to mark a break in a sentence in place of a semicolon or colon. In this context, dashes are often used for emphasis or to signal a change in tone.

There was no arguing with her—she was set in her opinion.

En dash vs em dash

As their names suggest, the em dash is approximately the length of the letter m, and the en dash the length of the letter n. Both are longer than the hyphen (-).

Em dash

The em dash is used for setting off information or marking a break in a sentence. No space should be used on either side of an em dash.

In the interrogation room, the detective questioned the suspect—who sat shifting nervously—on his whereabouts the night of the incident.

En dash

Strictly speaking, the en dash has a different function, but you will often see it used in the same way as an em dash. In this context, the en dash takes a space on either side.

In the interrogation room, the detective questioned the suspect – who sat shifting nervously – on his whereabouts the night of the incident.

This usage of the en dash is especially common in British English, while the em dash is more prevalent in American English. Style guides differ on this point, but your main focus should be on consistency.

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En dash to indicate range

The en dash is also used to indicate a range of numbers or a span of time. You can read it as representing “to” or “through”.

The company had a successful 2018–2019 fiscal year.
This job demands frequent evening and weekend work in addition to regular 9:00am–5:00pm hours.
The document was heavily redacted, with pages 46–52 removed altogether.

Consistency with dashes

Whether you choose to use em dashes or en dashes, pick one and use it consistently. A common mistake is using both forms in the same sentence or text, or spacing the punctuation incorrectly.

  • Jeff Bezos–who is the founder, chairman, CEO, and president of Amazon — is one of the richest people in the world.
  • Jeff Bezos—who is the founder, chairman, CEO, and president of Amazon—is one of the richest people in the world.
  • Jeff Bezos – who is the founder, chairman, CEO, and president of Amazon – is one of the richest people in the world.

Dashes vs hyphens

Hyphens are used to link words together. They should not be used in place of dashes.

  • The door slammed shut behind him – and that was the last I saw of him.
  • The door slammed shut behind him—and that was the last I saw of him.
  • The door slammed shut behind him – and that was the last I saw of him.
Is this article helpful?
Amy Luo

Amy has a master’s degree in History of Art and has been working as a freelance writer and editor since 2014. She is passionate about helping people communicate clearly and effectively.

2 comments

Lou Benders
June 15, 2015 at 5:25 PM

Dear Dorothy,

Writing guidelines on when to use a hyphen is definitely a good idea!

In your case carbon-based is indeed correct. This is a compound adjective, just like well-known, good-looking, bad-tempered, carbon-neutral and custom-built.

Most compound adjectives are hyphenated and some are not. Sometimes hyphens are used in such adjectives to avoid that the meaning becomes ambiguous. This is the case with '100 year old men', which could be referring to 100 men that are a year old, or to men that are 100 years old.

However, whether you should use a hyphen or not, is not always clear. Thus, this is some food for thought!

We will definitely think about writing an article on the subject!

Reply

dorothy de kok
June 3, 2015 at 5:54 PM

How about some guidelines on when to use a hyphen and when not? e.g. is it carbon-based material or carbon based material? I go with the first one, but there is nothing here to support my opinion.
Really love your articles!

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