I am editing the text of a medical document. We are describing the function of the heart.

METS (metabolic equivalent for task) = the number of calories and the amount of oxygen you consume at rest. So, if you are exercising at 5 METS you are working 4x as hard as you would be at rest and consuming 4x the amount of oxygen and burning 4x the amount of oxygen.

In this text our subject matter expert is describing a multiplier of 4 times. Is this text set correctly or should we instead use the Unicode multiplier symbol ?

METS (metabolic equivalent for task) = the number of calories and the amount of oxygen you consume at rest. So, if you are exercising at 5 METS you are working 4✕ as hard as you would be at rest and consuming 4✕ the amount of oxygen and burning 4✕ the amount of oxygen.

We are already using to denote multiplication elsewhere.

BMR (Women)

BMR = 10 ✕ weight (kg) + 6.25 ✕ height (cm) – 5 ✕ age (years) – 161

But I do not recall seeing "4✕" used before so I am asking here.

Best argument for "4✕" is that this is read as "four times" a quantity.

Best argument for "4x" is that this is interpreted as "4 ✕ x" which means "four times a given quantity x". And that is written more simply as "4x" meaning "four times x".

What is the best practice in this situation?

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    in my experience 4x means 4 times a quantity. A capitol X is not used. To remove ambiguity you can say "4 times" or even better "four times" – Webster Aug 2 '17 at 15:05
  • I've only ever seen the Unicode 'x' used in equations. I believe it is more standard to use a regular 'x' in sentence structure. To me, they both represent 'times' or 'multiply'. – Ashlee Palka Aug 2 '17 at 15:08
  • I second that, in my experience, a lowercase x would be used – Manly Aug 2 '17 at 15:08
  • Are you following a specific style guide (e.g. APA, Chicago, etc.)? Usually things like this are addressed. For example, you woud write out fully numbers under ten (e.g. four times vs. 4x) – curious Aug 2 '17 at 15:18
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    If you are writing a style guide, please advise against half-baked mathematical operations, i.e., “burning 4✕ the amount of oxygen” → “burning 4 times the amount of oxygen”. – Wrzlprmft Aug 2 '17 at 15:39

I see only two reasons to use x instead of ×:

  • You have to expect that × will cause technical problems.
  • You consider it not worth the effort.

Otherwise, × is Unicode’s intended character for this purpose. Making it distinct from the letter x is advantageous for searching and other automatisms (of course, this most often works if everybody uses it).

For people using a screen reader or other tools, × increases accessibility. For example, if you write 4×4, you don’t want the screen reader to say four iks four but four times four.

Finally, good font designers can make use of the fact that x and × are used for entirely different purposes and design them accordingly increasing readability:

  • × will be centred with uppercase numbers, x won’t.

  • In case of lowercase numbers, the letter x may optically blend in with the numbers.

  • × will spaced in such a way that it is easier to recognise as a mathematical operator and not as part of the number.

  • Decorations such as serifs won’t be applied to ×, which makes it easier to recognise as a cross.

  • In case of blackletter or handwriting typefaces, x may not look like a cross at all.

Here are some examples to illustrate the above:

enter image description here

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  • This is all absolutely true, but it is a list of reasons why you should use × in mathematical operations (which the question makes it clear the document already does); it fails to note that in the specific context that is being asked about here, the answer is that neither x nor × should be used. There's no mathematical operation, so there should be no mathematical operator at all. ‘Times’ is just a regular word here. – Janus Bahs Jacquet Aug 2 '17 at 21:12

In normal paragraph text, preferred style is to write this out in words, "four times", unless for reasons of space or clarity you are compelled to shorten it to "4 times" or worse, "4×".

Don't use "4x" with a lower-case X. This would perhaps be understood, but it looks like an x, not a multiplication sign, and is wrong.

And don't use "4✕". That's a 'dingbat' character U+2715 that prints much larger than desirable in some fonts, and won't even be present in many fonts. Dingbats are a historical hang-over from the Zapf Dingbats font of the '70s, '80s and '90s. Use the standard multiplication sign × U+00D7, if anything.

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It depends on what kind of document you are typesetting and who the audience is. If you are also including other typesetting fine-tuning of the same kind (en/em dashes, open type figures, custom spacing and so on) and you expect the audience to really observe and appreciate these subtle differences, it would make sense to use the dedicated × character.

Then, if the document is using a lot of formulas like the the 'BMR (Women)' you mentioned, these make more sense with the dedicated × character.

Otherwise, in real life and in normal body text flow people have probably just gotten used to reading a normal '4x' when referring to a multiplier.

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