UK TeX FAQ -- question 157

### The comma as a decimal separator

If you use a comma in maths mode, you get a small space after it; this space is inappropriate if the comma is being used as a decimal separator. An easy solution to this problem is to type (in maths mode) `3{,}14` instead of typing `3,14`. However, if your language's typographic rules require the comma as a decimal separator, such usage can rapidly become extremely tiresome. In such cases it is probably better to use the icomma package. The packages ensures that there will be no extra space after a comma, unless you type a space after it (as in `f(x, y)`, for instance), in which case the usual small space after the comma appears.

`icomma.sty`
  Distributed as part of macros/latex/contrib/supported/was.tar.gz