How can I get bold math symbols?

Question

To make Latin-letter variables bold I can use e.g. \mathbf{a}, but while putting Greek letters or symbols such as \nabla inside \mathbf doesn't cause any errors or warnings, it also doesn't do anything else.

What is the best way to make bold math symbols, in particular Greek letters and \nabla?

Answer 1

The AMS Short Math Guide recommends the \boldsymbol and \pmb commands (and suggests that you use the bm package for the former to get a more powerful version than provided by amsmath).

Answer 2

In my experience, there is no single best way. Therefore Table 582 on page 270 of the Comprehensive LaTeX Symbol List comes in really handy. (Visited June 4, 2023)

Answer 3

With unicode-math you can use \symbf{<characters>} which works for both Greek and Latin letters. (In versions of unicode-math older than 0.8 the \symXXX macros didn't exist, but you could \mathbf{<characters>} directly.)

Compile with xelatex or lualatex.

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{XITSMath-Regular.otf}
% or a different font:
%\setmathfont{texgyrepagella-math.otf}
\begin{document}
\( AaBb∇αβγ \) \par
\( \symbf{AaBb∇αβγ} \) \par
\( \symrm{AaBb∇αβγ} \)
\end{document}

Answer 4

Another possibility is \boldmath, though I would prefer \boldsymbol of amsmath as well. \unboldmath switches back to the normal math font.

Answer 5

If you use the package bm you can do $\bm{a}=\bm{\alpha}$ etc.

Answer 6

While \bm and \boldmath are some good options in LaTeX, modern packages for XeLaTex can give a lot more control over the fonts from the very beginning, without the need to use commands different from the standard \mathbf that every one expects naively to work the first time one tries to write bold italic characters.

In XeLaTeX (part of TeXLive), the package fontspec gives a lot of freedom when dealing with fonts. If you want even more flexibility for mathematical input, you can try using the package unicode-math (that is built on fontspec). Nevertheless you will find the \bm and \boldsymbol traditional commands don't work. You can nonetheless specify how you want it to deal with your bold math symbols using an option while loading the unicode-math package. \usepackage[bold-style=ISO]{unicode-math} will give the recommended italic bold math symbols for both greek and latin characters, while \usepackage[bold-style=TeX]{unicode-math} will give upright latin characters. This is explained in the unicode-math documentation .

This minimal working example:

%run this with XeLaTeX!!
\documentclass{article}
\usepackage[bold-style=ISO]{unicode-math}
%\usepackage[bold-style=TeX]{unicode-math}
\setmainfont{XITS}
\setmathfont{XITS Math}


\begin{document}

This is common math $O(\log n)+O(\lambda,\,\epsilon)$

This is bold and italic $\mathbf{O(\log n)}+\mathbf{O(\lambda,\,\epsilon)}$ where it must :)
\end{document}

gives

Answer 7

Use the command \boldsymbol{YOUR_SYMBOL}

Answer 8

In order to have just one command for both bold text and bold math, one can use the solution suggested on LaTeX Community. Editing this solution slightly in order to incorporate the bm package, one could use the following.

\usepackage{bm}
\newcommand*{\B}[1]{\ifmmode\bm{#1}\else\textbf{#1}\fi}

Answer 9

Observe how ugly \pmb is in the following example, compared to \bm:

\documentclass{article}
\usepackage{amsmath, bm}
\begin{document}
$$\Psi_n \pmb{\Psi_n} \bm{\Psi_n} \boldsymbol{\Psi_n} \Psi_n$$
\end{document}

Answer 10

My solution (the one that I use) is the \mathversion{bold} and \mathversion{normal} commands.

This piece of code is not a MWE —however, it shows how to use them:

\mathversion{bold}
\section{Behavior of $f$ as a function of $\lambda$}\label{sec:1}
\mathversion{normal}

And now, imagine that \mathversion{bold}\textbf{we want to put some
text in bold, and that this text contains some inline equation such as
$\sum_{j=0}^{t-1}{{p_\mathrm{y}(\lambda=2)}^j}$.}\mathversion{normal}

Hope it helps.

Answer 11

Another option:

\documentclass{article}
\newcommand{\boldm}[1] {\mathversion{bold}#1\mathversion{normal}}
\begin{document}

There is a normal symbol, $p_1$. Now, a bold symbol: {\boldm $p_2$}. It works!

\end{document}

Output:

Answer 12

You can use physics package and write any math symbol in boldface by using command \vb{} inside mathmode, e.g. $\vb{\Psi}$ will yield Ψ.

Answer 13

The unicode-math package supports several commands for bold symbols beyond what have been mentioned in previous answers, including \mathbf, \symbf, \symbfup, \symbfit and \boldsymbol. It requires LuaLaTeX or XeLaTeX.

If you load a math font that has a bold version, unicode-math will load it as version=bold. There are now several, including XITS Math, Libertinus Math, and KP Math. It is also possible to load any math font with \setmathfont[version=bold].

Here’s a brief MWE that uses \boldmath, \symbf and \boldsymbol. Note that \mathbf will use the bold weight of the main text font, \symbf will use the mathematical bold letters and numerals defined in the Unicode Mathematical Alphenumeric Characters block, and \boldmath, \mathversion{bold} and \boldsymbol will use the bold math font (if there is one).

\documentclass[varwidth = 10cm, preview]{standalone}
\usepackage{mathtools}
\usepackage[math-style=ISO]{unicode-math}
\usepackage{microtype}

\defaultfontfeatures{ Scale = MatchUppercase }
\setmainfont{Libertinus Serif}[Scale = 1.0, Ligatures = Common]
\setsansfont{Libertinus Sans}
\setmonofont{Libertinus Mono}
\setmathfont{Libertinus Math}

\begin{document}
\section*{\boldmath Reasoning from \(\symbf{A} \vee \symbf{B}\)}

If we have \(\symbf{A} \vee \symbf{B}\) and \(\symbf{A}\), disjunctive syllogism
(classically known as \textbf{\textit{modus ponendo tollens}}, and also known
as \textbf{disjunction elimination} or {\boldmath \(\vee E\)}) is the rule
that lets us conclude \(\boldsymbol\therefore \symbf{B}\).

\end{document}

There are several ways to tweak this behavior. By default, \mathbf renders bold capital letters upright and bold lowercase letters italic, but [math-style=ISO] makes italic the default for everything, including regular-weight uppercase Greek. You can change only the behavior of bold uppercase letters with bold-style=ISO] or [bold-style=upright]. You can also specify \symbfup for bold upright or \symbfit for bold italic.

Answer 14

Like in some other answers, I use \mathversion{bold}, but I've never had to use \mathversion{normal} to reset the font. In particular, I use the following commands:

\newcommand{\allbf}[1]{\textbf{\mathversion{bold}#1}}

to get bold characters for both text and math.

And with the article class, to get bold math in addition to the usual bold text in any section title (at any section level):

\let\B@startsection\@startsection
\renewcommand{\@startsection}[6]{\B@startsection
{#1}{#2}{#3}{#4}{#5}{\mathversion{bold}#6}}