I am facing the following typography problem:

In a scientific article I am writing, there naturally occur instances, where there are math symbols and their meaning scattered in prose text, e.g. "The input voltage u is given, as well as the inductivity L and the moment of inertia M, where [\n] i refers to the current through the motor." ("[\n]" symbolizes a potential newline character inserted by my teypesetting system.)

On some ocassions, my typesetting system sometimes inserts a line break before the math symbol, putting the symbol at the start of a new line.

Note, that I am not talking about the start of a sentence, but just the start of a line.

My supervisor tells me, this is bad practice, and that lines must not start with a mathematical symbol (1).

I know how to avoid this in my typesetting system (LaTeX), but I have never heard that rule before, so I am curious about learning more about it.


  1. Can you guide me to a reference work to confirm or abnegate (1)?
  2. If not a reference work, can you give an article where this is being written about?

If this is language-dependent: I'd like to know in particular about German, British English and American English.


I am not well-versed in typography literature, and my online search has not brought any meaningful insights for me.

  • Hi. In English the only similar "rule" I am aware of is that sentences should not start with a numeral, but should be written out as a number in full. So "25 years ago, ... should be written as "Twenty-five years ago, ...". I don't see how this fix could be applied to maths symbols though. Perhaps you should ask your supervisor if your organisation has a style guide available. That might be the source of this rule.
    – Billy Kerr
    Jul 31, 2023 at 11:31
  • Thank you for your input, but I am the one responsible for designing a style guide, so currently there is none. My supervisor brought this up in a discussion, but since I am designing the guidelines, I need to know more precisely. I remember being taught that sentences must not start with symbols, aside from numerals, but I'm lacking a solid reference to this as well.
    – marc
    Jul 31, 2023 at 11:40
  • I see. Might be worthwhile looking at some other maths publications, or see if you can sneek a peak at some other organisation's style guide for inspiration. Sorry, but I'm no mathematician, and writing a maths paper is probably a bit different from general writing under normal circumstances. Also it might be helpful for you, there actually is a Mathematics Stack Exchange.
    – Billy Kerr
    Jul 31, 2023 at 11:43
  • I'm not sure if a question like this would be on topic there, but I suppose you could ask in their chat room first.
    – Billy Kerr
    Jul 31, 2023 at 11:49
  • 1
    There's also academia.stackexchange.com Jul 31, 2023 at 17:27

2 Answers 2


I think this questions is very interesting, and despite my lack of experience in this particular field, I'd like to help if possible. So after a little research online I managed to find a style guide for the American Mathematical Society: Available here. Hopefully this will be of some help to you.

Here's an interesting quote that seems relevant to your quandary.

From Part 1, Chapter 1, 12.5 Wording (page 81)

Try to avoid reference numbers, variables, equation numbers, and mathematical expressions as the first word in a sentence.

So, this would seem to be a recommendation rather than a rule, at least as far as this particular style guide is concerned.

I'll leave you to peruse the rest of the guide at your own leisure, but there are various parts that describe what to do where equations might break at the end of a line, etc.


I did not hear about a rule like that before.

Anyhow theres a rule that you should not split numbers with their units (like "1 meter"). This should apply here as well with the variable names and letters.

Also as there's a risk that the letters are read as part of the text, especially in your example the "i" it be best to visually set them appart from the rest of the text.

Most applications allow you to add a non-breaking space. ( )

"The input voltage u is given, as well as the inductivity L and the moment of inertia M,
where i refers to the current through the motor."

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