# How to put some comment-like text in a formula?

I have the following formula:

$$\bot \dashv\vdash \bot \land A /* not derivable */$$


But the phrase /* not derivable */ doesn't show correctly. For example there is space between / and *, but no space between not and derivable.

How can I fix that?

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You seem to be using plain TeX so I'll stick to that, you can use \hbox to get back into text mode

  $$\bot \dashv\vdash \bot \land A \qquad \hbox{/* not derivable */}$$

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$\bot \dashv\vdash \bot \land A$ not derivable