Suppose that I would like to say "Let f(x) be an N-times differentiable function."
Should it be "N-times" or "N times", and why?
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2Does this answer your question? Student t-distribution: why the dash { 'hyphens: numerals and single letters Hyphenate numerals or single letters and the words they modify: e-cigarette e-commerce e-learning S-hook T-shirt U-turn 1,2-dimethylbutylene 2,4-D ...' [BtB Public Works ... Translation Bureau]– Edwin AshworthCommented Aug 7, 2021 at 10:59
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Thanks, but no. t-distribution refers to a compound thing, so there must be a hyphen. This is different with the question (or is it?).– nullCommented Aug 7, 2021 at 11:00
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Yes it does, within the remit of ELU. [n times] or [n-times] is a compound word with a letter as first element, as are 'T-shirt' and 'e-commerce'. If there is here (as DjinTonic's research shows) a very different bias, this is because of the mathematical preferences involved, and this question is better asked on Mathematics.SE. Lexico gives the hyphenated spelling of the adjective two-time: [adj] [attributive] ... ‘a two-time winner of the event’. (Though I'm sure the open compound is also used.)– Edwin AshworthCommented Aug 7, 2021 at 11:23
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@EdwinAshworth I've edited my answer. I believe two-time and two times/two-times behave differently. Few would disagree with the hyphen for time.– DjinTonicCommented Aug 7, 2021 at 12:02
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1@EdwinAshworth Edited.– DjinTonicCommented Aug 7, 2021 at 14:33
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2 Answers
No hyphen seems to be much more common in math, as this Google Books search for "N-times differentiable function" indicates, with six out of six examples hyphenless. (Looking at more pages in the search I see one example with a hyphen and dozens without.) If I were writing this, my instinct would be to use a hyphen.
This may have to do with how we modify times:
"...and will meet with n times as many ethereal particles , and will impinge upon each particle with n times greater velocity" ref
...the lifting force becomes n times greater than it was... ref
I think we agree that a hyphen is needed for a six-time Olympic champion.
However,
... making her a four times champion of the world. ref (1918)
and
...he was not destined to join Harry Vardon and Braid as four-times champion ref (1908)
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Yes, I feel it more natural to use hyphen, though I don't why the literature go without hyphen.– nullCommented Aug 7, 2021 at 11:09
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1,2-dimethylbutylene is prescribed. And Lexico gives the hyphenated spelling of the adjective two-time: [adj] [attributive] Denoting someone who has done or experienced something twice. ‘a two-time winner of the event’. This question is thus obviously about non-quotidian English usage; this belongs on Mathematics. Commented Aug 7, 2021 at 11:21
I would write it as
n–times differentiable function
Why the en-dash?
Because n and times are compound adjectives describing function. It makes no sense to say
? n function
or
? times function;
both the n and the times must be modifying function together to make sense.
Here are some helpful citations:
Student t-distribution: why the dash [sic, EA; hyphen]
When should compound words be written as one word, with hyphens, or with spaces?
Why is n lowercase?
When n refers to an arbitrary integer in writing about mathematics, it is written in lowercase and (usually) is italicized (and put into a math font).
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Dashes are rarely used in compounds (and there's no possibility of one here). Some use the en-dash to form larger compounds involving shorter open or hyphenated compounds [Grammarly]. Commented Aug 7, 2021 at 11:56
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