This past month’s CopyChat was on proper dash usage. It turns out that there are three main dash styles: hyphens, en-dashes and em-dashes. Here is a quick rundown of how each is to be properly used:

Hyphens
A hyphen is the shortest of the dashes. On a keyboard it is implemented using the key directly to the left of the zero key. A hyphen is used within compound words or as part of a non-continuing numbers, such as phone numbers.

Examples: 555-123-1234, co-worker, editor-in-chief

En Dashes
An en-dash is about twice the width of a hyphen, or the width of a capital N—hence its name. An en-dash is also sometimes denoted as two hyphens without any spacing between them, and is therefore sometimes referred to as a double dash. An en-dash denotes a range, and is most often used with numbers such as dates or times. An en-dash should be typeset “tight”—meaning without any spaces before or after the dash. On a Macintosh computer, you can type an en-dash by holding option-hyphen.

Examples: 8:30am–10:00am, January 1–10

Em Dashes
An em-dash is about three times the width of a hyphen, or the width of a capital M—hence its name. It is sometimes denoted as three hyphens without any spacing between them. An em-dash denotes a pause in thought, a parenthetical statement, afterthought statement or is added for emphasis. It is traditionally set “tight”—meaning without any spaces before or after the dash. However, AP style specifies that a space should be used before and after the dash. Unless one must follow the formatting specified in a specific style guide, it seems that since either tight or spaced formatting seems excepted, consistent formatting is the most important thing. On a Macintosh computer, you can type an em-dash by holding shift-option-hyphen.