# Bold italic vectors

I am trying to display vectors as bold and italic. The command \mathbf sets the letters non-italic. I also googled a bit and stumbled upon \mathbf{\em y} or \mathbfit{y}, which all didn't work.

I hope someone can help me on this.

• I've marked your inline code with backticks . (You don't have to sign with your name since it automatically appears in the lower right corner of your post.) – Hendrik Vogt Mar 28 '11 at 8:30
• Your command \mathbf is quite good at least for the unit vectors \mathbf{i}, \mathbf{j} and \mathbf{k}. – Name Nov 19 '17 at 16:25

It depends on the math font, but the bm package can handle most of them. The usage is then $\bm{y}$

• This works. But it is not working within multicolumn environment like the following case, \multicolumn{2}{c}{$\bm{a\:(\si{\angstrom})}$} but it works for \multicolumn{2}{c}{$\bm{\alpha_T\; (K^{-1})}$}. How to solve this? – cosmicraga Sep 12 '13 at 5:30

There is also \boldsymbol{} from the package amsbsy (loaded by amsmath). See this question for a discussion of the advantages and disadvantages of each command.

• Cool answer. In my case no need to load extra packages (like bm), because when working with math stuff, I usually use the amsmath. :) – loved.by.Jesus Jan 8 '16 at 15:15

What I did, is to declare my own command for a vector, well its pretty basic, but you can add other features, like an arrow.

\newcommand{\vect}[1]{\boldsymbol{#1}}


And the usage:

\vect{X} = \left[x_1,x_2,\ldots,x_n \right]^T


returning:

The answer depends on the math fonts you are actually using. For the standard fonts and as long as you use only letters and numbers this should work:

\documentclass{scrartcl}
\DeclareMathAlphabet      {\mathbfit}{OML}{cmm}{b}{it}

\begin{document}
$a=\mathbfit{a}$
\end{document}


A few years late to the game, but since people are still linking to this question, here’s an update.

The \mathbfit command is defined in both unicode-math and the legacy isomath package. In either case, it will match the current font, or the package allows you to load a different bold italic math alphabet.

There is also a semantic \vectorsym command in isomath, which sets letters in bold italic but digits in bold upright.

In unicode-math, you would want to use \symbfit for bold italic math symbols (as \mathbfit matches the text font, not the math font). There are no bold italic mathematical digits in Unicode, so you would need to use \symbfup` for digits instead.