The two dashes, en (-) and em (—), are slightly different in size and use. They are often misused, so you can set yourself apart by knowing how to use them properly.
En dashes are the width of an –n and show continuing times or dates.
I’ll be signing autographs from 9-10 p.m. between July 1-22.
Em dashes are the width of an –m and used for:
- inserting additional information (usually unexpected but important) into a sentence.
- The man—fat by all standards—was convinced he should wear a Speedo;
- lists when the list in is the middle of a sentence.
- The men she loved most—her father, her husband, and now her lover—had all betrayed her.
- Write em dashes using two consecutive dashes together (–) with no space between the dashes and letters.
- If you are worrying about the difference between a hyphen and an en dash, don’t. Should you be in a situation where one must be used over the other, you’ll probably have an editor or publisher who will do this for you.