Does anyone know how to make a subscript on the left hand side in LyX in a formula?


3 Answers 3


In LaTeX, without using any additional package, you could use

${}_x F_x$

to write xFx. Using this as the baseline approach, inside a math formula, insert a subscript to "nothing", followed by the "middle symbol", followed by another subscript.

enter image description here

  • 1
    This is not very good, since if you have something before the first "_{x}", e.g. A _{x}F_{x} then it would be typeset as if you have a subscript for A
    – Ur Ya'ar
    May 22, 2018 at 11:54
  • @UrYa'ar: There are ways around that. Do you have any suggestions? Perhaps not using LyX? ;)
    – Werner
    May 22, 2018 at 19:22
  • 1
    One way it to put a {} before. Another is to implement \prescript in a macro, I gave a detailed answer below.
    – Ur Ya'ar
    Jul 12, 2018 at 8:32

The mathtools package defines \prescripts which is supposed to give the right spacing for left super/sub-scripts.The syntax of the command is \prescript{<sup>}{<sub>}{<arg>}. To implement it in LyX one should define a macro as follows: enter image description here To get it, on the "TeX" box you write the following string (don't copy-paste as it won't work. While typing the script LyX will change e.g. \{ into the correct form of {})

 \prescript\{\#1 \{\#2 \{\#3

and in order for it to preview nicely, write in the "LyX" box

^\#1 _\#2 \#3

of course you can skip either the sup or sub script argument, but you still need to have an empty '{}' for it, e.g

enter image description here

Note that if you get a compilation error you need to tell LyX to load mathtools via Document->Settings->Math options.


Here's a solution that I found to be easier than Werner's, and not requiring the extra packages and macros that Ur's solution needs:

Simply press CTRL+SPACE to make a half-space, which allows you to make the desired subscript:

enter image description here

Then delete the halfspace!
Unlike Werner's solution, I never needed to click anything. My hands never had to leave the keyboard!

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