使用两列进行枚举

Question

我想要一个包含两列的枚举。第一列报告属性的名称，第二列可以是多行文本，并且应该正确缩进。因此，第二列的文本应该遵循文档的边距。

像这样：

\begin{enumerate}
\item[] \textbf{Diagonal}, if all its elements outside the main diagonal are equal to zero, that is $\forall i\neq j$, $a_{ij} = 0 $ 
\item[] \textbf{Scalar}, if all off-diagonal elements are zero and all on-diagonal elements are equal 
\item[] \textbf{Identity}, if it's scalar and the elements on its main diagonal are all equal to 1, that is $\forall i$, $a_{ii} = 1$ 
\item[] \textbf{Lower triangular}, if all the entries above the main diagonal are zero, that is $\forall i > j$, $a_{ij} = 0$ 
\item[] \textbf{Upper triangular}, if all the entries below the main diagonal are zero, that is $\forall i < j$, $a_{ij} = 0$
\end{enumerate}
Below, a brief summary of the matrix operations used:
\begin{enumerate}
\item[] \textbf{Addition}: If $A$ and $B$ are matrices of the same size then the sum $A$ and $B$ is defined by $C = A + B$, where 
\begin{equation}
c_{ij} = a_{ij}+b_{ij} \quad \forall i,j
\end{equation}
\end{enumerate}

使用 leandriis 的链接，这是我得到的

“Diagonal” 后面有 \quad\quad，我想缩进第二列“Scalar” 中的所有文本是正常结果。

Answer 1

某个longtable环境可能非常适合您的排版需求。

您可以根据（a）第一列的宽度和（b）文本块的整体宽度来调整第二列的宽度。

\documentclass{article}
\usepackage{array,longtable,ragged2e}
\newcolumntype{P}[1]{>{\RaggedRight\arraybackslash}p{#1}}

\begin{document}
\noindent
A matrix is said to be
\begin{longtable}{@{} >{\bfseries}l P{0.6\textwidth} @{}}
Diagonal & if all its elements outside the main diagonal are equal to zero, that is $\forall i\neq j$, $a_{ij} = 0 $\\
Scalar & if all off-diagonal elements are zero and all on-diagonal elements are equal\\
Identity & if it is scalar and the elements on its main diagonal are all equal to 1, that is, $\forall i$, $a_{ii} = 1$ \\
Lower triangular & if all the entries above the main diagonal are zero, that is, $\forall i > j$, $a_{ij} = 0$ \\
Upper triangular & if all the entries below the main diagonal are zero, that is, $\forall i < j$, $a_{ij} = 0$
\end{longtable}

\bigskip\noindent
Below, a brief summary of the matrix operations used:
\begin{longtable}{@{} >{\bfseries}l P{0.7\textwidth} @{}}
Addition & If $A$ and $B$ are matrices of the same size then the sum of $A$ and $B$ is defined by $C = A + B$, where
\begin{equation}
c_{ij} = a_{ij}+b_{ij} \quad \forall i,j
\end{equation}
\end{longtable}
\end{document}