Even subscript height

Other things being equal, TeX will aim to position subscripts and superscripts in places that « look good ». Unfortunately, it only does this for the sub- and superscripts of each atom at a time, so if you have

$ X^{1}_{2} X_{2} $

the second subscript will appear higher, since the first has moved down to avoid the superscript; the effect can be noticeably distracting:

![[faq-images1.png|faq-images1.png]]

You can avoid the problem, for a single instance, by

$ X^{1}_{2} X^{}_{2} $

here, the dummy superscript has the requisite « pushing down » effect:

![[faq-images2.png|faq-images2.png]]

While this technique does what is necessary, it is tedious and potentially error-prone. So, for more than one or two equations in a document, the LaTeX user is advised to use the subdepth package, which forces the lower position for all subscripts.


Source: Even subscript height