in Design
Hyphens, en dashes and em dashes
Three horizontal lines of different lengths, each with its own job. How hyphens and dashes are used in British books, and where they go wrong.
There are three common horizontal marks in text, and a keyboard makes only one of them easy to type. The result is that hyphens and dashes are among the most frequent errors in manuscripts. They are easy to fix, provided everyone agrees which mark is which.
The hyphen
The hyphen is the shortest. It joins words and parts of words: compound adjectives such as a well-known face, some compound nouns, certain prefixes, and words broken at the end of a line. It never has spaces around it, except in a construction such as pre- and post-war, where it stands in for a repeated word.
Whether a compound is hyphenated, closed up or written as two words is a matter of style and dictionary choice, and it changes over time. A house style or a standard dictionary settles these questions for a given book.
The en dash
The en dash is longer than a hyphen, traditionally about the width of a capital N, or half an em. It has two main uses.
First, it indicates a range, standing for to or through: pages 45–62, 1914–18, Monday–Friday. It is set closed up, with no spaces, when joining single items. If a range is introduced by from or between, it should be written in words instead: from 1914 to 1918, not from 1914–18.
Second, it shows a relationship between two things of equal weight: the London–Paris train, a parent–teacher meeting, a cost–benefit analysis. Here a hyphen would suggest a single compound, while the en dash keeps the two elements separate.
In much British publishing, a spaced en dash is also used as the parenthetical dash, the mark that sets off an aside in a sentence – like this – or introduces an afterthought.
The em dash and the minus sign
The em dash is longer again, traditionally the width of the type size, or roughly a capital M. In American publishing, it is the usual parenthetical dash and is set without spaces—like this. Some British publishers use closed-up em dashes in the same way, but spaced en dashes are more common in British books.
In fiction, em dashes are often used for interrupted speech, marking the point where a speaker is cut off. A spaced or closed dash at the end of the interrupted sentence, before the closing quotation mark, is common. Many styles use an ellipsis instead for speech that trails away rather than stops, which keeps the two effects distinct.
A 2-em dash or 3-em dash is sometimes used to indicate missing letters or a repeated author’s name in a bibliography. These are specialised uses and are governed by the relevant style guide.
The minus sign is a fourth mark that is often confused with the others. It is usually designed to match the plus sign in width and vertical position, and it should be used in mathematical expressions and negative numbers. A hyphen used as a minus looks too short and sits too high or low in many faces.
Getting them right
Manuscripts almost always contain a mixture: double hyphens standing in for dashes, hyphens used for ranges, spaced hyphens used as parenthetical dashes. These should be regularised during copy-editing, according to the house style, before typesetting.
The typesetter then needs to check two further points. Spaced dashes should be set with a space that will not let the dash begin a line, since a dash at the start of a line looks detached from the text it belongs to; a non-breaking space before the dash is the usual solution. And the dash in a range should not be allowed to break across lines, which would leave half a date on each.
Dashes are simple, once the rules are clear. The difficult part is applying them the same way on every page.