This answer suggests using p-type column and \newline command.
However, once you realize that p-type column is just typesetted in a \parbox (basically a vbox in plain TeX), a paragraph break works.

So:
\documentclass{article}
\begin{document}
\begin{tabular}{p{3cm}p{3cm}}
hello
world&hello
world
\end{tabular}
\end{document}
I'm not sure why nobody have suggested that
given how ⟨blank line⟩ is preferred over \newline or \\ in normal text.
Perhaps it's because of semantic meaning -- you're unlikely to include a whole paragraph in a table cell. But if you do it may make sense.
E.g. the example below includes 2 paragraphs in each table cell.
\documentclass{article}
\usepackage{fullpage}
\begin{document}
\begin{tabular}{p{7cm}p{7cm}}
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit,
vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum
gravida mauris. Nam arcu libero, nonummy eget, consectetuer id,
vulputate a, magna. Donec vehicula augue eu neque. Pellentesque habitant
morbi tristique senectus et netus et malesuada fames ac turpis egestas.
Mauris ut leo. Cras viverra metus rhoncus sem. Nulla et lectus
vestibulum urna fringilla ultrices. Phasellus eu tellus sit amet tortor
gravida placerat. Integer sapien est, iaculis in, pretium quis, viverra
ac, nunc. Praesent eget sem vel leo ultrices bibendum. Aenean faucibus.
Morbi dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla.
Curabitur auctor semper nulla. Donec varius orci eget risus. Duis nibh
mi, congue eu, accumsan eleifend, sagittis quis, diam. Duis eget orci
sit amet orci dignissim rutrum.
Nam dui ligula, fringilla a, euismod sodales, sollicitudin vel, wisi.
Morbi auctor lorem non justo. Nam lacus libero, pretium at, lobortis
vitae, ultricies et, tellus. Donec aliquet, tortor sed accumsan
bibendum, erat ligula aliquet magna, vitae ornare odio metus a mi. Morbi
ac orci et nisl hendrerit mollis. Suspendisse ut massa. Cras nec ante.
Pellentesque a nulla. Cum sociis natoque penatibus et magnis dis
parturient montes, nascetur ridiculus mus. Aliquam tincidunt urna. Nulla
ullamcorper vestibulum turpis. Pellentesque cursus luctus mauris.
&
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit,
vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum
gravida mauris. Nam arcu libero, nonummy eget, consectetuer id,
vulputate a, magna. Donec vehicula augue eu neque. Pellentesque habitant
morbi tristique senectus et netus et malesuada fames ac turpis egestas.
Mauris ut leo. Cras viverra metus rhoncus sem. Nulla et lectus
vestibulum urna fringilla ultrices. Phasellus eu tellus sit amet tortor
gravida placerat. Integer sapien est, iaculis in, pretium quis, viverra
ac, nunc. Praesent eget sem vel leo ultrices bibendum. Aenean faucibus.
Morbi dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla.
Curabitur auctor semper nulla. Donec varius orci eget risus. Duis nibh
mi, congue eu, accumsan eleifend, sagittis quis, diam. Duis eget orci
sit amet orci dignissim rutrum.
Nam dui ligula, fringilla a, euismod sodales, sollicitudin vel, wisi.
Morbi auctor lorem non justo. Nam lacus libero, pretium at, lobortis
vitae, ultricies et, tellus. Donec aliquet, tortor sed accumsan
bibendum, erat ligula aliquet magna, vitae ornare odio metus a mi. Morbi
ac orci et nisl hendrerit mollis. Suspendisse ut massa. Cras nec ante.
Pellentesque a nulla. Cum sociis natoque penatibus et magnis dis
parturient montes, nascetur ridiculus mus. Aliquam tincidunt urna. Nulla
ullamcorper vestibulum turpis. Pellentesque cursus luctus mauris.
\end{tabular}
\end{document}
By default there's no first-line-indent, so the appearance
should be identical to as if \newline is used.
Another solution: \shortstack (similar to the nested-tabular solution this does not require specifying explicit width)
\usepackage{makecell}and using\makecell{...\\...}is sufficient to get a linebreak in the cell. – luator May 11 '15 at 09:48pbox, this also works withadjustbox(\adjustbox{valign=t}{\makecell{content}}) – koppor Dec 14 '15 at 01:05Missing number, treated as zero.Illegal unit of measure (pt inserted).pdfTeX error: pdflatex.EXE (file futr8r): Font futr8r at 604 not found– maja Jun 14 '17 at 19:31\theadcommand actually decreases the font size of the cell? – Dr_Zaszuś Aug 02 '17 at 14:03theadtofootnotesize. If you want something else, you can redefine it globally or locally with, e.g.\renewcommand\theadfont{\normalsize}. – gusbrs Dec 21 '17 at 16:43\renewcommand{\cellalign}{l}(it will remain vertically centred), or, for some specific cells,makecell[l]{ ... }or\thead[l]{ ... }. – Bernard Feb 26 '18 at 13:04\makecel{ ... \\ ... }does not preserve vertical alignment – deps_stats Nov 04 '18 at 01:04\cellalignin the preamble, so it's valid for the whole document, or using an optional argument, such as\makecell[l] { ... \\ ... }to have all lines left-aligned, for instance. – Bernard Nov 04 '18 at 02:32\makecellwith the default automatic line break and custom line breaks to prevent the table having a greater width than the page? – mhellmeier Jan 12 '21 at 14:02l,rorc). For automatic line breaks, you can use a nested tabular with a fixed width column. – Bernard Jan 12 '21 at 14:16makecellis old and not supported.\theadsometimes produces unexpected result. Nowadays just use\parbox,\pbox, or\Block{1-1}fromnicematrix. – facetus Feb 28 '21 at 04:31makecell, except used withcolortbl. Your solution requires determining at least an approximate cells width. I prefer\Centerstack,or\Vectorstack, fromstackengine, whenmakecelldoesn't work smoothly. – Bernard Feb 28 '21 at 10:56\makecell{...\\...}is aligned center w.r.t the first part. – Manjoy Das May 14 '21 at 19:55renewcommand\cellalign}{lb}to have all \makecell bibottom and left aligned. If you want it only for specific cells, use an optional argument:\makecell[lb]{…}. – Bernard May 14 '21 at 20:06\newlinecommand where you want a line break. – Bernard May 17 '21 at 16:13\\can take an optional argument to add some vertical spacing. The simplest solution would be to add a pair of braces around the brackets, like this:\thead{text \\ {[text]}}\\. – Bernard Feb 02 '22 at 22:32