5. Hyphens, en dashes, and em dashes
The next major change we need to discuss is dashes. Typewriters only have one—the hyphen. Type has three—the hyphen, the en dash, and the em dash. All three have very specific usage rules.
Hyphen: This is the character used to hyphenate words at the end of a line and to create compound words. For example, 10-point is the normal point size for book publishers’ body copy. In fact, hyphens are used in no other places.
So, you have a couple keystrokes to learn because en and em dashes are used quite a bit during the creation of normal copy.
En dash: This dash is an en long. It is used with numbers, spans, or ranges. For example, pages 24–39, 6:00–9:00, or May 7–12. It is a typo to use a hyphen in these cases. The keystroke for an en-dash is Option+Hyphen (PC: Ctrl+Num–).
A special case: In rare cases, hyphens and en dashes need to be mixed for clarity. Last week, when talking about the width of a hair space for InDesign was one example. It seemed to me to be easier to read and more understandable written as one–twenty-fourth with the en dash between the one and twenty-fourth. This is the typographer’s decision to make.
Em dash: This dash is an em long. It is a punctuation mark. The keystroke for an em-dash is Option+Shift+Hyphen (PC: Ctrl+Alt+Num–). Grammatically it is stronger than a comma but weaker than a period. Other than that, there is no standard anymore.
American English is a living language in constant flux. These changes have accelerated in recent years. In many cases, there are no rules anymore. Em dashes are used more every year. In many ways they are very helpful—but traditionalists tend to have knee-jerk reactions to anything outside the grammar books (written decades ago).
Typewriters use a double hyphen for the em dash. This is an embarrassing error to professionals. In fact, it is one of the sure signs of amateurism.
Spacing around em dashes: this is wide open to personal opinion. I was taught a thin space before and after, currently I am using no additional spacing (especially in this blog where a thin space is not available. However, I have heard enough other suggestions to realize that usage varies widely.
Em dashes automatically: Word converts two hyphens to an em dash if you have auto-formatting turned on. You can set up the same conversion in InDesign by adding an auto-correction item. Be careful of Word’s automatic conversion. When you place it into InDesign these converted characters often come is as Ö or something even more strange.
Finally, do not think you will not be caught. Hyphens are about a thin space wide. They are higher above the baseline than en or em dashes. Also, they are commonly slanted up with little swashes on the ends (although you see swashes on all three in Contenu at the beginning of this post).