# How do I define a smaller space in Math mode?

These are all the standard math mode spaces in Latex. The smallest one, defined by `\,`, has a length of 3 mu. My question is very simple: can I define smaller spaces in math mode, for instance one of 1 or 2 mus? If possible, how do I do so?

• `x \mkern 1mu x` – David Carlisle Apr 2 '18 at 23:50
• Thank you for your comment. Could you please turn it into an answer, with a bit of an explanation, for me to accept it? – Héctor Apr 2 '18 at 23:51
• `\mskip1mu` too. If what you want is to make all of those `\,` smaller, you can do `\thinmuskip=2mu`. – Manuel Apr 2 '18 at 23:54

the math analogues of `\kern` (for fixed spaces) and `\hskip` (for stretchy space) are `\mkern` and `\mskip` which take `mu` units where a `mu` is 1/18 em

so you can do

``````\$x \mkern 1mu x\$
``````

but it is rather rare to use explicit space rather than use the named spaces such as `\,` which is `\mkskip\thinmuskip`

`\thinmuskip` isn't a fixed length, it is given an initial value of

``````\thinmuskip=3mu
``````

but if you are using a math font other than computer modern a slightly larger or smaller amount may be more suitable, so a global setting such as

``````%\thinmuskip=3mu
%\medmuskip=4mu plus 2mu minus 4mu
%\thickmuskip=5mu plus 5mu

\thinmuskip=2mu
\medmuskip=3mu plus 2mu minus 3mu
\thickmuskip=4mu plus 4mu
``````

would give tighter spacing

• Using XeLatex, I set \thinmuskip=1mu directly after defining \documentclass. I can change it to whatever I want, no change in the PDF. – Ralf H Mar 2 at 18:27