# Incidence Symbol for Geometry

My professor invented a symbol for when a line and a point are geometrically incident. I added a picture and wanted to ask if someone knows how to write this in LaTex? It is a small line with a dot in the middle.

\documentclass{article}
\usepackage{tikz}

\newcommand{\incid}{%
\tikz{%
\draw[line cap=round,line width=0.13ex] (0,0)--(3ex,0);
\fill (1.5ex,0) circle (0.5ex);
}}

\begin{document}
$(P, G, \incid)$
\end{document}


• This is perfect, thanks. Is there an easy way to make the gaps between any input and the symbol a little wider on both sides? Commented Apr 23, 2022 at 17:23
• No need for an answer, I figured to add \hspace in the command. Commented Apr 23, 2022 at 17:25

This should be a relation symbol. It can be obtained with the sequence

\relbar \joinrel \mathrel{\!\bullet\!} \joinrel \relbar


The \relbar command typesets a minus sign considered as a relation symbol; \joinrel is a small negative space considered as a relation symbol. The \bullet is made into a relation symbol, with reduced sidebearings.

\documentclass{article}
\usepackage{amsmath}

\newcommand{\incidence}{\relbar\joinrel\mathrel{\!\bullet\!}\joinrel\relbar}

\begin{document}

$(\mathcal{P},\mathcal{G},\incidence)$

\end{document}


Here's another solution that uses the method here for superimposing symbols.

\documentclass{article}

\usepackage{amsmath}
\usepackage{amssymb}

\makeatletter
\newcommand{\superimpose}[2]{%
{\ooalign{$#1\@firstoftwo#2$\cr\hfil$#1\@secondoftwo#2$\hfil\cr}}}
\makeatother

\newcommand{\incidentsymb}{%
\mathpalette\superimpose{%
{\rule[0.5ex]{1.2em}{0.5pt}}%
{\text{\textbullet}}%
}%
}

\begin{document}

$(\mathcal{P}, \mathcal{G}, \incidentsymb)$

\end{document}


The easiest way to do this is:

{-}\!{\bullet}\!{-}


Curly braces are used to suppress natural spaces; \! is a negative space.

Of course, you can use \newcommand:

\newcommand{\incid}{{-}\!{\bullet}\!{-}}


A bit thicker line:

{\bf-}\!\!{\bullet}\!\!{\bf-}


• +1, but, please, note that \bf has been deprecated for about 30 years. In the particular case it does exactly nothing anyway. Commented Apr 24, 2022 at 15:51

Just for fun, one way that works only with luatatex. With xelatex work adding \ensuremath before \bullet, but with pdflatex also failed miserably.

\documentclass{article}
\usepackage{graphicx}
\newcommand\incidence{\mathrel{\rotatebox{90}{\bullet\kern-.4em|}}}
\begin{document}
$(\mathcal{P}, \mathcal{G}, \incidence )$
\end{document}