\documentclass{article}
\begin{document}
\section{Normal Use}
\begin{tabular}{cc}
t & $m$ 
\end{tabular}

\[\begin{tabular}{cc}
t & $m$ 
\end{tabular}\]

\section{Perverse Use}
\[ \begin{array}{cc}
m & $t$
\end{array}\]

\[ \begin{array}{cc}
\mbox{t} & \mbox{$m$}
\end{array}\]

\[ \begin{array}{cc}
\mbox{t} & \mbox{$m$, $n$}
\end{array}\]

\section{Very Perverse}
\[ \begin{array}{cc}
m & $\hbox{$m$}$
\end{array}\]

\end{document}
