Dashes and hyphens

Last revised by Daniel J Bell on 5 Jan 2022

Dashes and hyphens are used all over Radiopaedia.org and should be used in a particular way to ensure consistency.  

Dashes and hyphens

In content typeset for printing, there are distinct differences between the following:

  • minus sign: used exclusively to represent a minus sign
  • hyphen: used to connect words in hyphenation
  • en-dash (width of an n): used to connect numbers or compound words
  • em-dash (width of an m): used instead of commas and parentheses

This contrasts with internet usage (including Radiopaedia) where the minus sign on the keyboard is often used for all of the above.

Minus and hyphen

The minus sign and hyphen scenarios above should be obvious use-cases.

Please also see Spelling and punctuation article for use of hyphens with prefixes.


When using the en-dash on Radiopaedia.org, we follow recognized standards (Chicago Manual of Style 1) and state that there should be no space on either side of the dash:

  • numeric ranges: incidence is 4-16%
  • compound words: T2-weighted 
    • routine hyphenation of compound words/phrases is discouraged, in general "less is more"
  • combinations of imaging modalities: PET-CT

In publishing, the longer dash (em-dash) is employed without surrounding spaces. On Radiopaedia.org, because the majority of people would not be able to add the em-dash, we have taken the pragmatic approach of replacing it with a " - ", which is a space, then a minus sign, then space. It should be used in place of a comma or parenthesis:

  • the use of the em-dash replaces normal parentheses - as can be seen here - when in the central part of the sentence 

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