Hyphens and dashes

Hyphen help: what’s the difference between a dash, a rule and a hyphen?

posted in: writing | 0

Before I re-trained as a proofreader and copy-editor I had only a vague idea about the different lines, rules, hyphens and dashes that appear in print. My office career began at a time when typists were still using typewriters and carbon paper and anyone who made too many changes to a draft report quickly fell out of favour with the secretaries. There are three types of dashes or rules: hyphens, en or N rules, and em or M rules, increasing in size in that order (dashes and rules are the same!). Now that I have trained my eye to look for the difference between these different characters I find them quite easy to spot.


The names N and M rule or dash came about from the length of the typeface of a lower case n and an upper case M. 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. It’s easy to see how this could evolve into the modern hyphen. 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. When proofreading and copy-editing, I try to follow these general principles to achieve consistency.

The hyphen

In terms of size the hyphen is the smallest line – short and fat. It is used in printed materials to divide words at the end of a line (this type of word break is called a soft hyphen). Other uses where it’s important to use the hyphen rather than its wider cousins, the dashes, are:
 —In forming compound words or phrases, e.g. part-time, up-to-date
 —Pre-fixes or suffixes, e.g. non-negotiable, risk-averse
 —Written numbers from 21 to 99, e.g. thirty-three
 —Double-barrelled names, e.g. Ponsonby-Smythe

N rules or 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 rule has no space between the words or numbers it is ‘connecting’ and conversely the spaced N rule has one space each side. 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 related words such as on–off friendship.
The spaced N rule can be used as a substitute for other types of punctuation such as a comma, colon or semi-colon, or a pair of spaced N dashes can be used instead of brackets or paired commas. You’ll see that I used a spaced n dash in the first sentence of the paragraph about hyphens; the lines in front of the four  points in the list are M dashes.

M rules or dashes

The M rule, both closed and spaced, occurs more often in US publishing and Oxford style. I noticed it recently when reading Richard Dawkins’ The Selfish Gene, published by OUP. French publishers also seem to favour it to introduce each new line of direct speech. The M rule is used in the same situations as the spaced 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. As with any style effect, the key is to be consistent and not to over-use a technique. So if you’ve used spaced N rules in place of brackets don’t suddenly change to closed M rules, and don’t use either more than once in a sentence or it will be difficult to follow.


The hyphen is easy to find, 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. You can also use this tab to customise your own keyboard shortcuts. I’m running Word 2013 at the moment so the two keyboard short cuts I use are Ctrl+num minus for an N rule and Ctrl+Alt+num minus for an M rule.
Perhaps you’ll spot some of these differences when reading, or perhaps it sounds just a little bit too fiddly and pedantic. If you want to ensure that your written text is consistent or if you need any help with editing or proofreading your essay, paper or application form contact me for a free quote.

Hyphens and dashes
Hyphens, en rules and em rules