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Dashes: - vs. – vs. —

I know that there are many sources on the use of dashes both on tex.sx ( Dashes: - vs. – vs. — ) and in the real world (Wikipedia: Dash). But there are still cases where I do not know the correct dash to use.

Compound words
many-body nature
electron-electron interaction
ion-atom collision
higher-order terms
non-negligible amount
short-lasting event
quasi-adiabatic reaction

Slevin-type source
Maxwell-Boltzmann distribution


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marked as duplicate by Yiannis Lazarides, Werner, Marco Daniel, Stefan Kottwitz Mar 1 '12 at 14:48


In your examples they are all dashes. –  Yiannis Lazarides Feb 29 '12 at 9:47
@YiannisLazarides: Yes - what dash? (do you mean what is written in latex as a single minus: -?). If that is true, then maybe I should delete this question again!? –  Hans-Peter E. Kristiansen Feb 29 '12 at 9:54
Yes and delete the question it is a duplicate. –  Yiannis Lazarides Feb 29 '12 at 10:04
In my humble opinion, in your example, they should all be hyphens -. Dash -- or --- is used generally in a place of comma , or as an interval, like 2009--2011. In "classical" English typography, you don't put spaces around dashes---like just here; it is because English typography tends to make all the inter-word spaces equal, no matter whether there's a dash or comma between the words. "Modern" typography changes this rule, but me personally, I tend to use the "classical" one. –  yo' Feb 29 '12 at 10:07
@YiannisLazarides: I don't think it is a duplicate, - as the answer can not be found elsewhere. -but it is stupid, as I probably should have known the answer. I will delete it. –  Hans-Peter E. Kristiansen Feb 29 '12 at 10:10

2 Answers 2

up vote 10 down vote accepted

Here is Bringhurst's take.

Almost all of your examples should be hyphens. Most interword dashes should be hyphens. The exception, as Joseph pointed out in the comments is cases like Maxwell–Boltzmann. This is a case of two different people's names joined up, and perhaps needs distinguishing from Maxwell-Boltzman as a double-barrelled name. Although only the keenest, typographically attuned eye will spot the difference…

En dashes should be used for number ranges 34–42 without space. As a "phrase marker" – a kind of alternative to the parentheses – the en dash should have space either side.

The em dash can be used to introduce dialogue

— Like this?
— Yes, like this.

And as an indicator of interruption, like thi—

Longer dashes can be used for repeated names in bibliographies.

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I'm not sure that is correct for 'Maxwell-Boltzmann'. This is the combination of two names, and so the dash may be replaced by 'and'. That means it should be an en-dash. –  Joseph Wright Feb 29 '12 at 10:11
@JosephWright: Ohh - I was so close to deleting my stupid question, before you wrote this. - can you elaborate? –  Hans-Peter E. Kristiansen Feb 29 '12 at 10:15
@JosephWright I guess you're right. I don't know whether Bringhurst discusses this (I couldn't find anything in a cursory flick through) but I can see the value in the distinction. –  Seamus Feb 29 '12 at 10:20
I believe that a hyphen or an en-dash between names is just a question of personal taste (or editorial choice). I personally prefer the hyphen. –  egreg Feb 29 '12 at 10:20
@daleif: I think that Joseph Wright provides the answer: Barndorff-Nielsen--Shepard !? –  Hans-Peter E. Kristiansen Feb 29 '12 at 10:34

Some typographers suggest (i.e. they consider it a possible way to do things, not a compulsory one) that you can use en-dashes (--) when you are not using a compound word or expression, but two different words that are in some sort of logical relationship (opposition, link). So for instance: "ion--atom collision", "London--Washington relationship", but "non-negligible".

Also, you can use an en-dash if one the words is already a compound word: "Pulitzer prize--winning", but "Selvyn-type source" or "short-lasting event" (they are expressions, not words of their own). It may not apply when the "compound" word only has a prefix in it: "non-English-speaking".

The logic behind it is that you should use a longer sign when the link between the two elements of the phrase is weaker, and a shorter one when they are very much related. For the same reason, many (more) typographers recommend using an en-dash between digits that indicate a range (see Bringhurst p. 80--81, with a dash).

Note: Few typographers openly endorse this practice, and few talk about it at all – but it does not mean it should not be used. Matthew Butterick is one that does recommend it (Typography for Lawyers, p. 49).

Some people recommend it only insofar as you do not use em-dashes (---) in your document, e.g. for dialogues and asides.

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Reading the comments on Seamus' post: indeed the dash could also be used similarly between the names of two people, especially if one of them already has a hyphen in it. –  ienissei Feb 29 '12 at 10:49
@PeterGrill I'm adding a pointer to my answer to the duplicated question. –  Lover of Structure Jan 3 '13 at 11:24
