Hyphens, Em Dashes, and En Dashes

This is from a nice blog written by Nancy Tuten (see here) with my editing. This post is for my own record only. All credits go to the original post, and all mistakes remain mine.

The hyphen, the em dash, and the en dash are all horizontal marks of varying lengths. Each functions differently from the others. Below we define each mark, explain when to use them, and provide instructions for typing them on both PCs and Macs. (View mini-lesson video on this topic.)

The Hyphen

The hyphen is the shortest of the three marks, and we use it most commonly to combine words (making compounds such as “well-being” and “advanced-level,” for example) and to separate numbers that are not inclusive (in phone numbers and Social Security numbers, for example). Correct hyphenation is often a complicated issue. However, our focus is on the two kinds of dashes.

The Em Dash

When we hear the term dash, most of us picture the em dash. It is significantly longer than the hyphen. We use the em dash to create a strong break in the structure of a sentence. We can use these dashes in pairs, as we would use parentheses—that is, to enclose a word, or a phrase, or a clause (as we’ve done here)—or they can be used alone to detach one end of a sentence from its main body.

Dashes are particularly useful in a sentence that is long and complex or in one that contains a number of commas, as in this example:

• We bought markers, paper, pens, and tablets—all of which were on sale, of course—for our clients to use in the courtroom.

If we confuse the em dash with the hyphen, we make a sentence virtually impossible to read. If we had used a hyphen in place of each dash two sentences ago, it would seem as though we had hyphenated two pairs of words in the sentence: “tablets-all” and “course-for,” neither of which makes any sense.

Em Dashes, Parentheses, or Commas?

A good rule of thumb is to reserve em dashes for those places where the comma simply doesn’t provide a strong enough break. If a comma (or a pair of them) works, use it.

Parentheses tend to downplay an idea; they suggest that the information in them is helpful but not necessary. Em dashes draw attention to the information they enclose or set apart. Typically the writer is telling the reader that the information being set off by em dashes is important.

The En Dash

The en dash is slightly longer than the hyphen but not as long as the em dash. (A common myth holds that the en dash is, in fact, the width of a typesetter’s letter “N,” whereas the em dash is the width of the letter “M”—thus their names. In fact, an em is a typographical unit of measurement.)

The en dash means, quite simply, “through.” We use it most commonly to indicate inclusive dates and numbers: July 9–August 17; pp. 37–59.

Many people were not even aware of the distinction between the en dash and the em dash until the advent of word processors, when software programs enabled us to use marks of punctuation that once had been available only to professional printers.

Important: Spacing with Hyphens and Dashes

When using the hyphen, the en dash, or the em dash, most—but not all—style books advocate putting space neither before nor after them. The Associated Press style (always the outlier) insists on spacing both before and after the em dash.

One exception is, of course, when the hyphen is used as a minus sign. The other exception is with a hanging hyphen (see, for example, the word “nineteenth” in the phrase “nineteenth- and twentieth-century literature”). By definition, a hanging hyphen will have a space after it but not before it.

Typing the En Dash and Em Dash

The latex commands are:

• Hyphen: -
• En-dash: \textendash
• Em-dash: \textemdash

With the latter two, you will likely want to append {}, because they swallow following space.

Note that not all keyboards around the world are the same. Our readers outside the U.S. tell us that they don’t have the following shortcuts on their keyboards. That said, here are guidelines for typing on many keyboards:

• On both PCs and Macs, two hyphens (typed with no space before or after either of them) will convert to an em dash—the full-length one that most of us think of when we hear the word “dash.”
• We can also choose en and em dashes from a menu of symbols that do not appear on the keyboard. In Microsoft Word, for example, we can pull down the “Insert” window, click on “Symbol,” and go to the “normal text” window. The en and em dashes appear on the bottom row.
• In any software program that handles text, the em dash can be typed on an enhanced keyboard as Alt + 0151—that is, hold down the “alternate” key and, using the numerical pad on the right side of the keyboard, type the numbers 0151. The en dash can be typed as Alt + 0150.
• Mac users also have another option: For an em dash, simultaneously press the shift, option, and minus keys. For an en dash, press the option and minus keys.

British (and Canadian) Usage vs. American

British/Canadian style guides seem wildly inconsistent on the issue of the em and en dash. Some say to use the en dash instead of the em dash, while others go so far as to advocate using the hyphen, advice that would lead to confusion for readers, as we have noted above. Our British and Canadian readers—and, indeed, any English-speaking reader outside the U.S.—should consult the style manual to which they default. The esteemed Oxford University Press style guide explains how to use both the em and en dashes, so we can assume that at least this authoritative source advocates using both.