In some countries one use comma as decimal separator instead of a dot.

I ususally use:

%%%% Une vrai virgule pour les décimaux

and $3@2$ to obtain 3,2 instead of $3,2$ that gives 3, 2 <- a uggly useless space after comma

I just find this :


That replaces automatically a dot by a comma in math mode, but with the ungly useless space.

Is there a way to combine both technics to have an automatic sustitution with a proper comma ?

Edit Sorry !

It was obvious :

%%%% Une vrai virgule pour les décimaux

Could this code have boder effect ? Is there a better or other way to get this ?

  • 4
    Try to use the siunitx package. Here you can define your decimal-seperator (Denmark uses comma here as well) and use \num{3,2} in order to express your values. Note that the package can do alot more, check out the docs.
    – Argo
    Apr 27, 2014 at 8:30
  • 2
    The localisation options for siunitx are set in the document preamble, and thus can be changed in one place. Alternately, you could move them to a .sty file.
    – ChrisS
    Apr 27, 2014 at 8:39
  • 2
    Please, take a look at tex.stackexchange.com/questions/154916/…
    – user13907
    Apr 27, 2014 at 8:58
  • 3
    Try \gdef.{{,}} instead of \gdef.{,} to get rid of the extra space. Apr 27, 2014 at 9:02
  • 2
    There is a package icomma, improving the math spacings for comma.
    – user31729
    Apr 27, 2014 at 9:03

2 Answers 2


To answer your original question. You could redefine . to produce another symbol in math mode.


Here in a MWE


enter image description here

  • Yes, it's easier than using @ and because the only use of . in mathmode is decimal separator.
    – Tarass
    Apr 28, 2014 at 8:47
  • 1
    \mathchardef\period=\mathcode`. before \DeclareMathSymbol{.} is better, isn't it?
    – egreg
    Apr 28, 2014 at 9:27
  • @egreg Nifty, thank you :-) I added this to my solution. Apr 28, 2014 at 9:35

This is more simple syntax which working only in mathmode:


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