What is the proper way to put a dot over an indexed variable, like for Netwon's derivative notation? For typesetting reasons, I prefer \dot{x}_i, but my colleage argues that it's an operator on x_i and hence it must be \dot{x_i}, which looks hideous if the index is longer, like \dot{x_\text{max}}. It becomes ever worse since I want to typeset vectors in boldface using the bm package, but then the dot is boldface as well, and that is certainly incorrect. Who has some wisdom for me?

\newcommand{\vect}[1]{{\bm {#1}}}

Is it $\dot{x}_i$ or $\dot{x_i}$? What about $\dot{x_{max}}$? \par
And what about $\vect{\dot{x}_i}$ or $\vect{\dot{x}}_i$, 
or maybe better $\dot{\vect{x}}_\vect{i}$?


Which yields this: enter image description here

  • 4
    Tell your colleague to "stuff it", in a nice way, of course. May 19, 2021 at 14:52
  • 2
    Definitely \dot{x}_{<subscript>} and \dot{\bm{x}}_{<subscript>}
    – egreg
    May 19, 2021 at 15:08
  • 1
    \do{x}_i tell your colleague that typesetting is not mathematics. May 19, 2021 at 17:48
  • 1
    I’m voting to close this question because solved in comments.
    – Roland
    May 26, 2021 at 8:01

1 Answer 1


Thanks. I can answer my own question from egreg's and David Carlisle's answers:

Use \dot{x}_{<subscript>} and \dot{\bm{x}}_{<subscript>}, since typesetting is not mathematics.

  • This answer was already given by @egreg in the comments above.
    – Roland
    May 26, 2021 at 8:01
  • You can only close a question with an answer. That's why I gave it.
    – cxxl
    May 27, 2021 at 9:35
  • 1
    No, you can close any question, regardless of whether it has an answer or not. Furthermore, it would be nice to name the author of the answer and not just pretend to be its own.
    – Roland
    May 27, 2021 at 23:05

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