Dashes and hyphens are distinct characters with specific intended uses 1.
Consistency and ease of editing are given priority over what some consider to be the more correct, but much more difficult to maintain, approach to punctuation.
Thus, at Radiopaedia, a pragmatic approach is taken with the use of hyphens only instead of a combination of similar appearing characters, with some rules about spacing (see below).
On this page:
Hyphen ( - )
Produced simply with the hyphen/minus key. Uses, both formal and at Radiopaedia:
-
some compound words and prefixes, see spelling rules for details
some compound words, e.g. x-ray, follow-up, T2-weighted
prefixes, only if a duplicate vowel is present, e.g. extra-axial, but not in hypointense
isotope notation, e.g. carbon-13, C-13 (we do not use the 13C notation)
combinations of imaging modalities, e.g. PET-CT
double surnames, e.g. Marie Skłodowska-Curie
breaking up of words onto the next line (hyphenation), performed automatically by the word processor or web browser (not used at Radiopaedia)
En dash ( – )
Formal uses:
ranges of numbers or dates, without spacing e.g. 1857–1942, 5–10%
eponyms named after multiple authors, e.g. Guillain–Barré syndrome
a pause – or instead of parentheses – in a sentence, surrounded by spaces
At Radiopaedia we use a hyphen in all these situations, with identical spacing rules.
Em dash ( — )
Formal uses:
a pause—or instead of parentheses—in a sentence, without spacing
At Radiopaedia we use a hyphen surrounded by spaces, as if it were an en dash.
Minus sign ( − )
Formal uses:
mathematical notation
Minus sign has similar length to the en dash, but slightly different spacing, which makes it more readable in mathematical formulas.
At Radiopaedia we use a hyphen for the occasional, simple formulas in text. More complex formulas are best to be introduced as diagrams, where all the necessary formatting and punctuation should be applied.