Typesetting standards for subscripts

[TRB8985]

TL;DR Summary

Clarification on subscripts involving axes and whether they should be italicized.

Good afternoon,

I have a question about italicizing certain subscripts. Say we have the following kinematic equation:
$$ y_{i} = y_{f} + v_{i_y}t + \dfrac{1}{2}a_{y}t^2$$ Where the $i$ and $f$ subscripts are in reference to initial and final displacements, and the $y$ subscript is in reference to an acceleration along the y-axis.

In the sources I've seen from NIST, IUPAC, and others$^{1, 2, 3, 4, 5}$, the general standard seems to be that any italicized letter is a variable. Thus, in the case above, $i$ and $f$ would not be italicized, as they represent static values of initial and final displacements. My question concerns $y$.

In this situation, the y-axis (in whichever direction we have chosen it to be), does not change. Furthermore, the vertical acceleration in this simple example does not change, either. (9.80 m/s²)

Thus, I'm under the impression that the subscript $y$ would be upright as well. However, at the bottom of the first page in the typefaces document from NIST, I can see they're italicizing the z-coordinate in $\omega_{z}$. It's not entirely clear if this coordinate is italicized due to the value of $\omega$ changing as one moves along the z-axis, or if this references the z-axis itself. Hence, my confusion.

Is anyone familiar with such an example and know the correct way in which this should be expressed? Thanks!$^{[1]}$ Hughes, K. 2016 May 4. To italicise or not to italicize. Brushing Up Science. https://brushingupscience.com/2016/05/04/to-italicise-or-not-to-italicise/

$^{[2]}$ Vrijmoet, E. 2017 May 1. Eliot's LaTeX Notes for Science Writing. Georgia State University. http://astro.gsu.edu/~vrijmoet/latexnotes.html

$^{[3]}$ Boffin. 2011 Oct 30. Should subscripts in math mode be upright? Stack Exchange. https://tex.stackexchange.com/questions/33120/should-subscripts-in-math-mode-be-upright

$^{[4]}$ Beccari, Claudio. 1997. Typesettings mathematics for science and technology according to IOS 31/XI. TUGboat. 18(1). https://tug.org/tugboat/tb18-1/tb54becc.pdf

$^{[5]}$ Keramati, H. 2020 July 7. When to italicize in a math expression? LinkedIn. https://www.linkedin.com/pulse/when-italicize-math-expression-hamed-keramati/

 

[Wrichik Basu]

Do you even need to care whether single letter subscripts are italicized or not? For subscripts of more than one letter, I will generally wrap them using \mathrm{} because it looks better, like $\omega_\mathrm{max}$. But for one letter subscripts, will anyone even care? I believe the acceptance of your paper in a journal will not be affected if you have italicized a subscript that you shouldn't have. Every journal has typesetters, who will format those little things before publication if the paper is accepted.

 

[TRB8985]

Do you even need to care whether single letter subscripts are italicized or not?

Probably not, but personally, I think it's worth the effort to develop good typefacing habits on these things. I can understand if others don't, though.

I believe the acceptance of your paper in a journal will not be affected if you have italicized a subscript that you shouldn't have. Every journal has typesetters, who will format those little things before publication if the paper is accepted.

My mistake for not mentioning anything about this in my original post - it's not actually for a journal. More of a public project. I don't like the idea of communicating bad notation publicly and perpetuating something incorrect. Hopefully that makes sense.

 

[FactChecker]

It is good to know the popular standards, but you should always define such things in your document if they mean something significant. And if you are publishing somewhere, know their particular standards.

 

[berkeman]

I have a question about italicizing certain subscripts. Say we have the following kinematic equation:
$$ y_{i} = y_{f} + v_{i_y}t + \dfrac{1}{2}a_{y}t^2$$ Where the $i$ and $f$ subscripts are in reference to initial and final displacements, and the $y$ subscript is in reference to an acceleration along the y-axis.

I'm of little help with your italics question, but I did notice that you have $y_{i}$ and $y_{f}$ backwards in your equation.

 

[vela]

I'm of little help with your italics question, but I did notice that you have $y_{i}$ and $y_{f}$ backwards in your equation.

That should be $y_{\rm i}$ and $y_{\rm f}$.