Dashes are not the same as hyphens. An en dash is wider than a hyphen, and an em dash is wider than an en dash:
en dash: –
em dash: —
The terms en dash and em dash originated in the days when text to be printed was set in type by hand. Each letter and punctuation mark was cast on a separate piece of lead type. An en dash was a line the width of a letter n. An em dash was a line the width of a letter m.
Not all style guides agree as to the use of en and em dashes. This post will deal only with the use of the en dash as recommended in The Chicago Manual of Style.
According to Chicago, “the principal use of the en dash is to connect numbers and, less often, words.”
When used with continuing numbers, such as dates, times and page numbers, the en dash represents the words “up to and including” or “through.” For example:
The Great Depression (1929–1939) was the deepest and longest-lasting economic downturn in the history of the Western industrialized world.
Note: If the word from precedes a pair of dates or numbers, the dash is not used. Instead, use the word to. Likewise, if the word between precedes the pair, the word and is used instead of a dash. For example:
The Great Depression lasted from 1929 to 1939.
Carole Lombard appeared in 15 short films between 1927 and 1929.
Used with scores and directions, the en dash signifies the word to:
The Cubs defeated the Cardinals 8–3.
The Chicago–New York train leaves at 9 a.m.
State universities that have more than one campus use the en dash to indicate which campus is meant:
The University of Arkansas–Fayetteville
The University of Arkansas–Little Rock
The University of Arkansas–Fort Smith
Chicago notes that the en dash is sometimes used as a minus sign, but discourages this use because in the Unicode system, the minus sign and the en dash are distinct characters. Using a minus sign for an en dash “may hinder searches in electronic publications.”
Many writers still use hyphens to create dashes in their copy because they don’t know there’s a way to produce “real” en and em dashes in their word processing program. If you’re one of them, here’s the secret:
Windows users can make an en dash by pressing Alt+0150. To make an em dash, they press Alt+0151.
Mac users can make an en dash by pressing the Option key and the hyphen key. For an em dash, they press Option, Shift and the hyphen key.
Note: Posts about punctuation trigger passionate comments—more than just about any other kind. The readers’ comments on the following posts offer a wealth of information and differing opinions about the use of en and em dashes: