\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}
