\begin{table}%t8
\caption{\label{defd4hd}Definitions in the [${\rm D}4000$, $W_0(\rm H_{\delta})$] plane.} 
%\centering
\small
\begin{tabular}{c c c}
\hline \hline
Definition & ${\rm D}4000$ & $W_0(\rm H_{\delta})$ \\
\hline
PEV (passive) & ${\geq}1.4$ & ${\leq}5$ \\
SF (star-forming) & ${<}1.4$ & $\in$[0, 5] \\
SSB (short starburst) & ${<}1.4$ & ${<}0$ \\
\hline
\end{tabular}
\end{table}