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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


  • 1
    In your examples they are all dashes.
    – yannisl
    Feb 29, 2012 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!? Feb 29, 2012 at 9:54
  • Yes and delete the question it is a duplicate.
    – yannisl
    Feb 29, 2012 at 10:04
  • 1
    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, 2012 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. Feb 29, 2012 at 10:10

2 Answers 2


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.

  • 11
    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, 2012 at 10:11
  • 1
    @Seamus I don't believe that the visual distinction between Maxwell--Boltzmann and Swinnerton-Dyer would be really clear for the reader. Nevertheless, what's chiefly important is uniformity all along a document.
    – egreg
    Feb 29, 2012 at 10:27
  • 1
    But what does one do when you have a theorem named after its authors, and one of these already has a hyphen in his name. Say Barndorff-Nielsen and Shepard, how does one name their theorem (if they have one named after them).
    – daleif
    Feb 29, 2012 at 10:29
  • 8
    @daleif: I think that Joseph Wright provides the answer: Barndorff-Nielsen--Shepard !? Feb 29, 2012 at 10:34
  • 4
    That was what AMS answered when I asked. But in that case one would need to write all other compound names as X--Y, for consistency
    – daleif
    Feb 29, 2012 at 13:40

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.

  • 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, 2012 at 10:49
  • @PeterGrill I'm adding a pointer to my answer to the duplicated question. Jan 3, 2013 at 11:24

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