2 这个表格过长，如何自动换行？

做得极端点

\documentclass{article}
\usepackage{mathtools}
\begin{document}
  \begin{table}
    \centering 
    \begin{tabular}{lp{0.4\linewidth}}
      \hline\hline
      \multicolumn{1}{c}{\textbf{Notations}} & \textbf{Definition}                                                                                      \\ \hline
      $ W_{0} $                              & A matrix whose i,j elements are the length of the historical path from i to j, and no is 0               \\
      $ W $                                  & A matrix whose i,j elements are the weight of the historical path from i to j, and no is 0               \\
      $ I_{0}$                               & A matrix whose i,j elements are from $W_{n}$, changing the no-zero element to 1                          \\
      $ f(W,n) $                             & A function of $W$, details can be seen later                                                              \\
      $ \mathbf{e_{i}}$                      & Represents a column vector with only the i-th element being 1                                            \\
      $ \operatorname{tr}{e_{i}} $           & A converted column of $e_{i}$                                                                            \\
      $n_{0}(i,j) $                          & Representing the number of edges passed by the corresponding historical path that $W_{0,i,j}$ presenting \\ \hline\hline
    \end{tabular} 
    \caption{Notations Table} 
  \end{table} 
\end{document}