This resource is an archived version of the Readability Guidelines.
New wiki is at: readabilityguidelines.myxwiki.org
Go to the Hyphens and dashes page.
Recommendations
Hyphens
Hyphens are used to join words, like compound words, prefixes and compass directions, together.
- do not use a hyphen unless the word is confusing without it
- never add white spaces at both ends
- avoid using hyphens for time and date ranges, instead use "to"
Hyphens in compound words tend to disappear over time if the compound becomes widely used. Inter-networking became inter-net became internet. Coffee-maker is now often coffeemaker, brides-maid is bridesmaid. Consistency within a document or an organisation is probably more important than 'correctness'.
The same words will have hyphens when used as a compound adjective before a noun but not if they come after it. For example, first-class essay but the essay is first class. This is mainly to avoid ambiguity: the Oxford reference below says 'For example, 250-year-old trees clearly refers to trees that are 250 years old, while 250 year old trees could equally refer to 250 trees that are all one year old'.
Hyphens in prefixes have also tended to decline in recent years, so it's common to see colocate rather than co-locate, deregulate rather than de-regulate. Sometimes a hyphen is needed for clarity (re-cover and recover, coop and co-op).
Examples
- x-ray, full-time
- de-classify, post-war
- north-east, south-west
- thirty-four, sixty-seven
Dashes
Dashes are sometimes used as punctuation in sentences. There are two types, the en-dash and the em-dash. Avoid using an en-dash or an em-dash if you can replace it with commas or brackets.
The en-dash (–) is:
- wider than a hyphen, but narrower than an em-dash
- the length as the letter ‘n’
En-dashes should always have a space before and after if used in the middle of a sentence.
The em-dash (—) is:
- wider than the hyphen and the en-dash
- the length as the letter ‘m’
- very unusual in UK-English text: US-English uses an unspaced em-dash as a separator in text in places where UK writers would use a spaced en-dash.
Em-dashes should never have spacing before and after.
Usability evidence
'The Trouble With EM ’n EN (and Other Shady Characters)', 2001
Oxford Living Dictionaries 'hyphen' entry, 2010
"Does hyphenation increase readability?" 2012
The hyphen, University of Sussex, 2013
The dash, University of Sussex, 2013
'Perilous Punctuation: Use the Dash With Panache', 2015
Oxford Living Dictionaries 'em dash' entry, 2018
Hyphens dashes readability Google Scholar search results Google Scholar, October 2018
There's an interesting discussion on the UX Stack Exchange page here: https://ux.stackexchange.com/questions/62575/hyphens-or-en-dashes-which-are-more-readable-when-used-in-number-ranges-for-nor
The Graphic Design Stack Exchange has a thread too: https://graphicdesign.stackexchange.com/questions/12993/does-hyphenation-increase-readability
Nothing standing out on the readability issues in general but there are some good points about formatting, and other aspects of text presentation.
It looks like another example where there are preferences, but it is really a matter of style and preference - and of course, best tested with users if possible.
This from A List Apart digs deeper into the history and differences between the types of dashes and the implications for digital encoding them: https://alistapart.com/article/emen
I have edited the draft wiki to I think clarify some of the points. as Karl says, there's not a lot here that is susceptible to user testing and a lot that is about custom and practice.
On that, I have pointed out that em dashes are not really used in UK-English text these days, but lacked the courage to just delete the text about use of em dashes - so the draft text is now contradictory.
I am just wondering, given that for date ranges "to" is preferable to "-" for screenreading software, wouldn't "to" also be preferable to an en-dash for all the en-dash usage examples?
World War l (1914–1918)
2001–
pages 32–85
L5–S1 disc herniation
Blue Jays win 4–2 in the eleventh inning
VV
World War l (1914 to 1918)
2001 to
pages 32 to 85
L5 to S1 disc herniation
Blue Jays win 4 to 2 in the eleventh inning
I'm not massively versed on what screenreaders read out for en-dash, but it seems they read out either "dash" or nothing at all, which with a) would be disruptive to user's thought flow and with b) would impair the understanding. So "to" would always feel preferable, e.g. compare "pages 32 dash 85" / "pages 32 85" with "pages 32 to 85".
Incidentally, what do screenreaders read out for parenthesis? According to the article below, some say nothing. I tend to avoid parenthesis in my content, using en-dashes instead or restructuring the sentence. But I'm now thinking that for accessibility en-dashes should also be eliminated.
https://www.deque.com/blog/dont-screen-readers-read-whats-screen-part-1-punctuation-typographic-symbols/