Using Dashes

What is a dash? 

A dash is a mechanical tool used to separate elements of a sentence. There are two types of dashes: the en dash and the em dash. An en dash is only a singular dash, slightly longer than a hyphen, while an em dash is two dashes put together to form a longer one. 

An en dash is used to define ranges of numbers, dates, or times. 

Examples

I read pages 20–23 of the book for class. 

I am on vacation June 23–June 30. 

I worked from 9:00 AM–5:00 PM. 

An em dash is used to emphasize parenthetical material.

Parenthetical material is extra information about a noun that may make the sentence more clear but is unnecessary for the meaning of the sentence. Using commas or parentheses places less emphasis on the material. 

Example

Workplace stress — from long hours to fear of being down-sized — is reducing the productivity of the American white-collar worker. 

An em dash is used to set off appositives from the rest of the sentence.

An appositive is extra information about a noun that renames the noun in order to make the sentence more clear. Using commas or parentheses places less emphasis on the material. Em dashes can be used instead, sometimes to indicate a change in thought, tone, or feeling.

Examples

China — the most densely populated nation on Earth — has only about two percent of the land suitable for agriculture in the world. 

Her musical talent — genius is perhaps a more accurate word — is wasted by simply teaching and never performing.