I'm trying to write the following but in bold: $M_s$ so that the "s" becomes next to "M" but low and i have the following code:

\title{Fundamentals of informatics A4}
\author{some name}
\date{January 2018}

% some text

into a new Turing machine \textbf{$M_s$} with the following behavior:

%some more text


The problem is that the M_s wouldn't appear bold no matter what i try

edit1: \textbf{} works perfectly with just text but when using the dollar signs, it doesn't.

  • 6
    Well, \textbf is meant for text mode, not for content in math mode. You can try {\boldmath $M_s$} – user31729 Jan 11 '18 at 8:28
  • 6
    Use $\mathbf{M_s}$ for upright M or \boldmath $M_s$\unboldmath – user2478 Jan 11 '18 at 8:32

Use the bm package and type $\bm{M_s}$ to get what you want. The command \textbf is for ordinary text, not for mathematical text.


You could define a command that automatically bolds text and math:


However, your question seems like you just want to have the s as an index to M and don't necessarily want them in math mode, so you might want to use:

\textbf{$\text{M}_\text{s}$} %% requires \usepackage{amsmath}

If it's in text mode, use \textbf{}.
If it's in math mode, use \mathbf{}.

Here's the distinction:

into a \textbf{new} Turing machine $\mathbf{M_s}$ with the following behavior:

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.