# inconsistent compiling of bold symbols in LaTeX

I am new to LaTeX and I am writing up an assignment and having trouble with bold, subscripted symbols. I want to write a product between a vector c_j and a scalar R_jk. I want the vector to be bold, and I want the scalar to be normal, so I write:

\textbf{$c_{k}$}$R_{kk}$


The R_kk here comes out bold, and I'm not sure why. Even if I end the sentence after the c_k and then write $R_{kk}$, it still comes out bold. Earlier in the assignment I have a term alpha - R_kk, both scalars, so I write:

$(\alpha - R_{kk})$


and this looks fine. My goal is to write c_k R_jk, next to each other to denote a scalar-vector product, and to have the c_k bold and the R_jk normal. Currently I can't figure out how. Any ideas?

• $\mathbf{c_{k}}$$R_{kk}$ Oct 27, 2021 at 10:35
• I understand wanting “c” to be boldface, but the subscript shouldn't be, otherwise it would not denote the same thing as in R_{kk}. Oct 27, 2021 at 10:59
• That didn't work Oct 27, 2021 at 16:48
• To clarify, I want the c_k to be bold, and the R_kk not to be bold, that's the issue here. Apologies if that wasn't clear. Oct 27, 2021 at 17:01
• Nevermind! I had \boldmath earlier in the script, which was making all math bold. Thanks! Oct 27, 2021 at 17:03

\textbf{$c_{k}$}$R_{kk}$


\textbf sets the text font to bold but has no effect on math within that scope. A bold math variable should be \mathbf so

\documentclass{article}
\begin{document}
$\mathbf{c}_k R_{kk}$
\end{document}


• This didn't work :/ same problem Oct 27, 2021 at 16:49
• Yes it will work , I added a complete document to my answer and showed the result with a bold c @lcleary Oct 27, 2021 at 16:53
• No that R is still bold, try putting this $(\alpha - R_{kk})$, before that line. You will see that the R from what you have up there is bold compared to the one in this term $(\alpha - R_{kk})$ Oct 27, 2021 at 16:57
• To clarify, I want the c_k to be bold, and the R_kk not to be bold, that's the issue here. Apologies if that wasn't clear. Oct 27, 2021 at 17:01
• Nevermind! I had \boldmath earlier in the script, which was making all math bold. Thanks! Oct 27, 2021 at 17:03