# Which package defines \smash?

I sometimes see \smash used to control local vertical alignment. Which package defines it?

• To clarify: Googling for "latex which package defines smash" might lead one to suspect amsmath or mathtools as the answer. So, one reason for asking this question is to generate a reliable search result for future reference. Plus I still haven't worked it out myself yet :)
– Roly
Apr 16, 2014 at 7:28
• amsmath redefines \smash to accept an optional argument in order to be able to smash only the height or the depth of the box. Apr 16, 2014 at 9:50

\smash is a macro defined in both plain TeX and the LaTeX kernel.

You don't need to load any package to use it.

The \smash command is active by default. No package needed.

% arara: pdflatex

\documentclass{article}
\begin{document}
xxx
\fbox{\rule{1cm}{2cm}}
\fbox{\rule[-1cm]{1cm}{2cm}}
\fbox{\smash{\rule{1cm}{2cm}}}
\fbox{\smash{\rule[-1cm]{1cm}{2cm}}}
\fbox{\raisebox{0pt}[0pt][0pt]{\rule[-1cm]{1cm}{2cm}}}
\fbox{\raisebox{-1cm}[0pt][0pt]{\rule{1cm}{2cm}}}
\end{document}