How can I create a rectangle symbol?
This is U+25AD (▭) and available as \hrectangle
in unicode-math
(if using xelatex or lualatex) or stix
if using pdflatex
(and will be available in other font packages that cover the Unicode math blocks)
\documentclass{article}
\usepackage{stix}
\begin{document}
$a \hrectangle b $
\end{document}
A good occasion for \ooalign
, one of the best tricks in my toolbox:
\documentclass{article}
\usepackage{amssymb}
\newcommand{\rectangle}{{%
\ooalign{$\sqsubset\mkern3mu$\cr$\mkern3mu\sqsupset$\cr}%
}}
\begin{document}
$S(\rectangle)$
\end{document}
Experiment changing 3mu
for different ratios between width and height.
\documentclass[12pt]{report}
\usepackage{amsmath,amssymb}
\newcommand{\rectangle}{\fboxsep0pt\fbox{\rule{1em}{0pt}\rule{0pt}{1ex}}}
\begin{document}
$s\rectangle$
\end{document}