当我使用此代码时：
\documentclass{scrbook}
\begin{document}
The thermodynamics of the phase inversion process at constant temperature $T$ is described by the free enthalpy of mixing $\Delta G\textsubscript{\mathrm m}$, which is given by ...
\end{document}
我收到这个错误消息，虽然我会说使用 $...$ 时数学模式是开启的？！
> ! LaTeX Error: \mathrm allowed only in math mode.
>
> See the LaTeX manual or LaTeX Companion for explanation. Type H
> <return> for immediate help. ...
>
>l.5 ...mixing $ \Delta G\textsubscript{ \mathrm m}$, which is given by ... You're in trouble here. Try typing <return> to proceed. If
> that doesn't work, type X <return> to quit.
编辑：问题是\textsuperscript 。当我们使用_时，不再有错误消息。