Em dash

Also called long dash or mutton dash.

How to type it

Mac: Shift + Option + -. Windows: Alt + 0151 on the number pad.

Common uses

• An em dash sets off an interruption or an afterthought—like this—from the rest of a sentence.
• Writers use it where a pair of commas, parentheses, or a colon would also work.

Less common uses

• The em dash is named for the em, a unit equal to the type size and traditionally compared to a capital M.
• Some house styles close the dash up against the words, while others, such as AP style, put a space on each side.
• A double hyphen -- is the old typewriter stand-in for an em dash, which typewriters had no key for.