Letters and numbers have a different dimension in subscripts

I am writing in math mode symbols with long lists of subscripts, that can either be letters or numbers.

For example, I write something like

\begin{equation}
p_{51y_4y_3}
\end{equation}

to obtain This looks rather inelegant though. Have you got any suggestion on how to improve it?

• What do you want to obtain? Looks fine for me. The way you are writing, you have p on level one, 51y and y on level two, and 4 and 3 on level three. If you would like something different, please adapt your question. Jun 10 '14 at 11:39

The dimensions of numbers and letters are different. As the y is not as high as the 1 you have maybe got confused as it looks a bit like a subscript y. But it isn't. Please have a look on my examples. As we don't know, what you actually want to write, you may combine my solutions by your needs:

% arara: pdflatex

\documentclass{article}
\usepackage{mathtools}

\begin{document}
$p_{51 y_{4}y_{3}}$ means $p$ with subscript $51y_4$ and $y_3$.

If you prefer, you may write $p_{51\,y_4\,y_3}$, or $p_{51,y_4,y_3}$,

or $p_{51\cdot y_4 \cdot y_3}$, or $p_{(51 y_{4}y_{3})}$.

Or did you mean $p_{51y_{4y_3}}$?
\end{document} • Hi, in my opinion the issue is that the y's are lower than the numbers.. It might look better if they were aligned at the bottom.. Is there a way to do that? Jun 10 '14 at 13:36
• @Manuele Easiest and not distracting way would be to use uppercase Y's. Is that possible for you? You can raise each letter, of course, but will that really help? "1" will always be bigger than "y" in your paper. So why not here? If you still want me to align them, I will give it a try. Jun 10 '14 at 13:41
• @Manuele Maybe better than aligning would be to use old style numbers (not a recommendation from my side as it looks strange). The numbers 1 and 5 will be set only to the height of the y. See here: tex.stackexchange.com/a/29101 Jun 10 '14 at 13:45

Regarding the question in the title: Characters have different dimensions (and line thicknesses) at very small sizes. They're not simply scaled-down versions of the normal-sized characters. This is a deliberate decision by the fontmakers to improve legibility.

Regarding the inelegance of your equation: I can only suggest rewriting it to avoid the subscripts. More than one level of subscript is inadvisable, in my opinion. You might consider presenting the subscripts as function arguments, though I don't know whether this is workable in your particular situation.

p(5,1,y_4,y_3)