ich möchte bspw. das \beta im Textmodus kursiv darstellen.
\documentclass{scrbook}
\usepackage{amsmath}
\usepackage{array}
\usepackage{upgreek}
\begin{document}
$\beta$\\
$\upbeta$\\
\textit{$\upbeta$}
\end{document} Gruß
\documentclass{scrbook}
\usepackage{amsmath}
\usepackage{array}
\usepackage{upgreek}
\begin{document}
$\beta$\\
$\upbeta$\\
\textit{$\upbeta$}
\end{document} 
$\beta$
\newcommand*\textbeta{\ensuremath{\beta}}
\documentclass{article}
\usepackage{textgreek}
\begin{document}
\textbeta\ \textit{\textbeta}
\end{document}