[Tex/LaTex] How to adjust column width of a table

Question

I have a table in the following code:

\documentclass{revtex4-1}

\usepackage{amsmath}
\usepackage{mathrsfs}
\usepackage{multirow}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{bm}
\usepackage{tabularx}

\begin{document}
\begin{table*}
  \footnotesize
  \caption{\label{tab:dimensionlessnumber}
  Definitions and physical meanings of dimensionless quantities.}
  \begin{ruledtabular}
  \begin{tabularx}{\textwidth}{llX}
  \textrm{number group} & \textrm{Definition} & \textrm{Physical meaning}  \\
  \colrule
  Density ratio               & $D=\frac{\rho_1}{\rho_2}$
  & A measure of the ratio of the A to B densities            \\
  Reactive number             & $R=\frac{s\Delta p}{a b C}$
  & The ratio of two very different quantities, a measure of the rate of reaction (very complicated), different from another definition in the reference                         \\
  Non-dimensional non-trivial parameter & $N=bk/aC$
  & A measure of the non-trivial degree at another side       \\
  \end{tabularx}
  \end{ruledtabular}
\end{table*}

\end{document}

It gives

In this table,

1. The 2nd row of the 3rd column cannot be shown completely. Is there any way to
   automatically split the long entry in multi-lines with an appropriate column width so that text wider than the column width will be put on a new line?

2. The 3rd row of the 1st column was obviously longer than the length of others.
   I have tried \\ to break it on a new line. But in this way,
   the entry of the second column, e.g., the definition of $N$, will then follow the second row, see the next figure. Instead, I want it in the first row.

To solve the problem, I have used tabularx environment (with width set to \textwidth, as shown in the this question and the other question. I even used \footnotesize to reduce the font of the table. But the problems remain. Thanks for any suggestion!

Answer 1

Remove ruledtabular and use p type for the first column. Also to make the table a bit more readable, you can increase line spacing by \renewcommand{\arraystretch}{1.5}. Finally, instead of multiple \hlines, you may consider using booktabs for much better output.

\documentclass{revtex4-1}

\usepackage{amsmath}
\usepackage{mathrsfs}
\usepackage{multirow}
\usepackage{amssymb}
\usepackage{amsfonts}
\usepackage{bm}
\usepackage{tabularx}

\begin{document}
\begin{table*}
  \renewcommand{\arraystretch}{1.5}
  \caption{\label{tab:dimensionlessnumber}
  Definitions and physical meanings of dimensionless quantities.}
  %\begin{ruledtabular}
  \begin{tabularx}{\textwidth}{ >{\raggedright}p{10em} l X }
  \hline \hline
  \textrm{number group} & \textrm{Definition} & \textrm{Physical meaning}  \\
  \hline
  Density ratio               & $D=\frac{\rho_1}{\rho_2}$
  & A measure of the ratio of the A to B densities            \\
  Reactive number             & $R=\frac{s\Delta p}{a b C}$
  & The ratio of two very different quantities, a measure of the rate of reaction (very complicated), different from another definition in the reference                         \\
  Non-dimensional non-trivial parameter & $N=bk/aC$
  & A measure of the non-trivial degree at another side       \\ \hline\hline
  \end{tabularx}
  %\end{ruledtabular}
\end{table*}

\end{document}