`\boldmath`

& `\unboldmath`

¶Synopsis (used in paragraph mode or LR mode):

\boldmath \(math\)

or

\unboldmath \(math\)

Declarations to change the letters and symbols in `math` to be in
a bold font, or to countermand that and bring back the regular
(non-bold) default, respectively. They must be used when *not* in
math mode or display math mode (see Modes). Both commands are
fragile (see `\protect`

).

In this example each `\boldmath`

command takes place inside an
`\mbox`

,

we have $\mbox{\boldmath \( v \)} = 5\cdot\mbox{\boldmath \( u \)$}$

which means `\boldmath`

is only called in a text mode, here LR
mode, and explains why we must switch LaTeX into math mode to set
`v`

and `u`

.

If you use either command inside math mode, as with ```
Trouble: \(
\boldmath x \)
```

, then you get something like ‘`LaTeX Font Warning:
Command \boldmath invalid in math mode`’ and ‘`LaTeX Font Warning:
Command \mathversion invalid in math mode`’.