Did you know that the term hyphen comes from the ancient Greek hypó hén meaning ‘in one’ or ‘under one’ and referred to a small line placed under two letters to indicate they belonged to the same word? Subsequently, the little line migrated to halfway up the first and last letters of the word it is joining. But the hyphen isn’t the only type of horizontal line you might need to use in your writing. There are, in fact, three different types of dashes (or rules, as they are sometimes called): hyphens, en or n dashes, and em or m dashes, increasing in size in that order. In this post, I’ll look at where you might use each of these and how to insert them into your document.
N dash or M dash?
The names N and M dash came about from the length of the typeface of a lower case n and an upper case M. A small n is narrower than a large M, and the dashes are the same dimensions. Whereas, as mentioned above, the hyphen is usually used to join words or sometimes to divide them. These three types of lines have particular uses and meanings. Some are generally applicable rules, whereas others are more a question of preferred or imposed style. There are also variations between US and British publishing practice.
In terms of size, the hyphen is the smallest line – short and fat. Hyphenation can be a tricky subject, but there is some great tips in this OED article. Sometimes a hyphen is used in printed materials to divide words at the end of a sentence. This type of word break is called a soft hyphen. Other uses of the hyphen are:
- In forming compound words or phrases, e.g. up-to-date, bed-and-breakfast
- Creating a compound adjective, e.g. part-time job
- Pre-fixes or suffixes, e.g. non-negotiable, risk-averse
- Written numbers from 21 to 99, e.g. thirty-three
- Fractions, e.g. three-quarters, one-third
- Double-barrelled names, e.g. Ponsonby-Smythe
An N dash can be used instead of a pair of commas or brackets to set off a subordinate phrase, or as a substitute for other types of punctuation such as a comma, colon or semi-colon. The two particular uses of the N rule that I look out for as a proofreader are in a range of numbers or elements, e.g. 1939–1945, Monday–Friday, or age range 0–5 years. Another use, often overlooked, is to join two words of equal stature which are connected such as on–off friendship.
The M dash seems to crop up more often in US publishing and Oxford style. It’s also sometimes used in fiction dialogue, to introduce each new line of direct speech. The M dash is used in the same situations as the N rule—in place of commas, colons, or brackets, or at the end of the sentence to introduce a phrase or list. New Hart’s Rules suggests it adds a slightly informal, casual effect (not sure about that, I’ve seen plenty of examples I academic writing).
Spacing your dashes
You might have come across the terms closed-up and spaced. This simply refers to the spacing around the dash. So a closed-up N dash has no space between the words or numbers it is ‘connecting’ and conversely the spaced N rule has one space each side; the same goes for M dashes. This is a – spaced – dash; this is a closed—dash.
The hyphen is easy to find, usually right at the top of your keyboard usually next to number 0. There are no special keys for N or M rules. You can use various keyboard shortcuts, depending of which version of Word you have installed, or you can use the Insert tab—symbols—special characters. On Office 365 Word 2016 the keyboard short cut for an N rule is Ctrl+num minus (or Alt 0150) and for an M rule it’s Ctrl+Alt+num minus (or Alt 0151).
Look out for some of these differences when reading, or try using them yourself in your next document. Just remember to be consistent, so if you’ve decided to use a closed M dash style keep to this throughout, don’t change to a spaced n dash.