Today, we’re tackling one of the more delightful intricacies of the grammatical universe: the world of dashes.
Dashes come in three lengths: hyphens (-), en dashes (–), and em dashes (—). Generally, their lengths are indicative of how much “work” they have to do—in other words, the types of things that they’re joining together.
The hyphen—the shortest of the bunch—connects what the Chicago Manual of Style describes as “two things that are intimately related, usually words that function together as a single concept or work together as a joint modifier.” Some examples include phrases like: one-third, father-in-law, and fine-dining restaurant.
En dashes connect things that denote any sort of range, whether that’s in the form of distance, time, or amounts. For example: it’d be a April–June issue of a magazine, or pages 50–55, or 5–6 tablespoons. An en dash is also used when a joint modifier—like the “fine dining” in “fine-dining restaurant”—contains an open compound or a many-worded proper noun. (An open compound is made when an adjective and noun are combined to make a whole new noun, such as dining room, ice cream, full moon, etc.) So in the case of a phrase like “a living room–sized rug” or “a Brette Warshaw–style outfit,” you’d use an en-dash, since it’s doing the extra work of carrying an additional word along for the ride.
Finally, an em dash has many jobs. First off, it serves as a way to insert a separate thought or phrase into a sentence—like this. It also can stand in for something that is missing or left out, such as in a bibliography; instead of repeating an author’s name over and over, for example, three em dashes can stand in for it, with the rest of the bibliographic information coming afterwards. Em dashes can also serve as bullet points in any type of list.
I’ll stop us here, but if you’re interested in learning more about the wonderful world of dashes, I highly recommend checking out Chapter 6 in the Chicago Manual of Style.