I am using Palatino for the content and I have a problem displaying \chi in math mode. The problem happens when I have a roman formatting in math, e.g., vector **x**, **X**, and **χ**; the χ turns to some other character.

## The minimal example

```
\documentclass[12pt,oneside,english,titlepage, a4paper, fontsize=12pt]{scrbook}
\usepackage{mathpazo}
\usepackage{geometry}
\geometry{letterpaper}
\usepackage{graphicx}
\usepackage{amssymb}
\usepackage{epstopdf}
%show vectors in bold
\renewcommand\vec[1]{\mathrm{\mathbf{#1}}}
%end renew commands
\title{Brief Article}
\author{The Author}
\begin{document}
\noindent Three different systems of reference are used within this
work. Structural deformations are described in the Lagrangian or material
formulation. The corresponding Lagrangian coordinate system denoted
by $\vec{X}$ is associated with the particular material points. The Eulerian or
spatial system of reference denoted by $\vec{x}$,
in which the observer is fixed in space and looks at the fluid passing.
In the ALE description of the motion, a third reference system, denoted
by $\vec{\chi}$.
\end{document}
```

which produces the following image:

What I would like to have is this [1]:

How can I fix this?

[1] The difference is that I removed `\usepackage{mathpazo}`

from the top.

## Best Answer

As long as your vectors are only Roman or Greek letters, the following works

Your

`\mathrm`

serves no purpose. The problem is that there's no Greek letter in the font used by`\mathbf`

, so we resort to the`\bm`

macros of packagebm.CautionThis works only with one letter as the argument.An alternative can be simply

but Roman letters will be in boldface (math) italic.