Each week proofreader Hannah Jones discusses and offers a remedy to common problems we encounter when writing. Today she explains the difference between hyphens, en-rules and em-rules.
Types of dash
Not to be confused with hyphens (-), there are two main types of dash which each serve distinct purposes: the en-rule (–) and the em-rule (—). Historically based on the size of a capital M, an em-rule is twice the length of an en-rule.
While hyphens are used to link two or more words together (e.g. copy-editor) or to divide a word if it is too long to fit on a line, dashes can be used to punctuate sentences. The most common example of this is to set parenthetical matter – such as this – apart from the rest of the sentence. In this way, dashes can be used much like commas or brackets.
Note that using commas, brackets or dashes give subtly different tones. Commas are the most neutral, brackets give the impression of a whisper or an aside, and dashes create a more pronounced break.
Dashes are also useful when the parenthetical matter is lengthy. In such cases, dashes may be preferable to commas as they create a more visible division between long phrases, which increases the readability of the sentence.
Either en-rules or em-rules may be used parenthetically. It is worth noting, however, that em-rules are usually closed up, with no spaces either side—like this—while en-rules are commonly spaced – like this. The em-rule is often considered somewhat old-fashioned, and spaced en-rules can seem more elegant, but some house styles do prefer em-rules to be used. If you don't have a style guide to follow, just make sure you use one option consistently.
Additional uses of the en-rule (–)
The en-rule can also be used to indicate ranges:
In such cases, the en-rule is always closed up. Note that the en-rule replaces 'from … to': we can either say, for example, 'The club runs from Monday to Friday' or 'The club runs Monday–Friday'. As such, some people will object to usage such as 'The club runs from Monday–Friday'.
The en-rule can also be used to express a connection between words:
the author–reader relationship
the Kansas–Nebraska Act
a London–Rome flight
the Federer–Nadal rivalry
the Cooper–Hofstadter paper
Additional uses of the em-rule (—)
The em-rule can also be used to indicate an interruption in the same way that an ellipsis suggests trailing off:
‘I'm only trying to—’
‘I know exactly what you're trying to do.’
‘I won’t fall in the—’
Some style guides also use em-rules in references and bibliographies when an author has more than one work listed:
Smith, A. (2011)
Dashes and hyphens are often confused; for more information on hyphens and their uses, see my recent blog post.