\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{tabular}{llll}
Lorem ipsum dolor & sit amet, ei mei
paulo tation honestatis,
intellegam & accommodare ne vim, ut
mel solum putant
atomorum. Posse & dolores has ut,\\
prompta           & disputando & ne mel, ne
viderer ceteros
vel.            & No petentium
\\

reformidans mel.  & Quo no sale
natum, cu
pericula   & deterruisset
usu. Nec        & bonorum detracto\\
detraxit          & no.        & Ne sea doming   & deserunt.
\end{tabular}

\begin{tabular}{ll}
1 & 2 & 3
\\
& 4 & 5
\\
6 & 7
& 8\\
9 &
10
& 11
\end{tabular}
\begin{align}
1 & 2
3 & 4
5\\
6 &
7
8 &
9
\end{align}

% Example given by Uwe Brauer <oub@mat.ucm.es>.
% (https://lists.gnu.org/r/auctex-devel/2022-01/msg00055.html)
\begin{equation}
  \begin{aligned}
&n u m=\left[\begin{array}{ll}
2 & 25
\end{array}\right] \\
&d e n=\left[\begin{array}{lll}
1 & 4 & 25
\end{array}\right]
\end{aligned}
\end{equation}

% Another example given by Uwe Brauer <oub@mat.ucm.es>.
% (https://lists.gnu.org/r/auctex-devel/2022-02/msg00039.html)
\begin{align}
A
& =
\begin{bmatrix}
a & b \\
c & d
\end{bmatrix}
,\qquad
B =
\begin{bmatrix}
1 \\
0
\end{bmatrix}
, \\
C & =
\begin{bmatrix}
b_{1} & b_{2}
\end{bmatrix}
,\qquad D = 0.
\end{align}

% Next table tests filling with a control symbol \& inside a cell; the
% function `LaTeX-indent-tabular' now (March 2017) detects \&, see:
% https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26010
\begin{tabular}{llll}
Lorem ipsum dolor & sit amet, ei mei \&
paulo tation honestatis, \&
intellegam & accommodare ne vim, ut
mel solum putant
atomorum. Posse & dolores has ut,\\
prompta           & disputando & ne mel, ne
\& viderer ceteros
vel.            & No petentium
\end{tabular}

% Next tables test filling when & (column separator) character is
% missing in a row; the function `LaTeX-hanging-ampersand-position'
% now (March 2017) detects this and has a fallback, see:
% https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26032
\begin{tabular}{llll}
\multicolumn{4}{c}{Lorem ipsum dolor sit amet, ei mei} \\
& paulo tation honestatis,
intellegam accommodare ne vim, ut \\
& mel solum putant atomorum. Posse & dolores has ut, \\
prompta & disputando & ne mel, ne
\& viderer ceteros vel. \\
& No petentium
\end{tabular}

\begin{table}[tbp]
  \begin{tabular}{llll}
\multicolumn{4}{c}{Lorem ipsum dolor sit amet, ei mei} \\
& paulo tation honestatis,
intellegam accommodare ne vim, ut \\
& mel solum putant atomorum. Posse & dolores has ut, \\
prompta & disputando & ne mel, ne
\& viderer ceteros vel. \\
& No petentium
  \end{tabular}
\end{table}

\end{document}
