# Symbol about not orthogonality in LaTeX

I found this post, which explains orthogonal and not orthogonal symbols.

I was able quickly to find the orthogonal symbols as \perp, \upvdash etc., but not able to find a top line which strikes the sign from the top left to bottom right. One idea is to combine to symbols e.g., use one of the aboves and add the line in top of it. However I don't know how to do it.

• I'm not sure if I understood your question correctly, but if you want to negate \perp, just add \not before it, e.g., \not\perp. I hope it helps. Commented Sep 6, 2011 at 11:03
• I fully agree with that answer: addiction to symbols is dangerous; and \not\perp doesn't seem very useful to me. Commented Sep 6, 2011 at 11:18
• @egreg Why is addiction to symbols dangerous?
– N.N.
Commented Sep 6, 2011 at 15:27
• @N.N. I'll repeat what I said in chat. As a young aspiring mathematician I was fond of symbols and overused them; experience showed me that less symbols and more words may make the exposition clearer. In some papers one can find newly created symbols that are used only a couple of times: these are obvious signs of "symbol addiction". As another example, long descriptions of sets with X={x\in U:...} may almost always be improved by saying the set $X$ consisting of elements $x\in U$ such that ... Commented Sep 6, 2011 at 15:39
• In writing, you'll probably be better off being clear and using words, not symbols.
– lhf
Commented Jul 4, 2012 at 11:13

To negate the \perp (perpendicular) symbol, one could use the command \not\perp. However, IMNSHO, this negated symbol doesn't look all that good:

If you load the mathabx package, you get the command \notperp which looks pretty good, as does now the output of \not\perp. The same effect can be achieved if you load either the MnSymbol package or the fdsymbol package and use the command \notperp (same name used by both packages). Notice, though, that even if you load the MnSymbol of the fdsymbol package, the output of \not\perp still looks pretty bad, i.e., as bad as if you hadn't loaded any extra package at all.

Addendum: Following a request by the OP, here's an MWE that shows how to load the mathabx package and generate the symbol using the package's \notperp macro, as well as with \not\perp

\documentclass{article}
\usepackage{mathabx}
\begin{document}
$a \notperp b$, $c \not\perp d$
\end{document}


Next, here's an MWE that shows the use of the MnSymbol package to generate these symbols:

\documentclass{article}
\usepackage{MnSymbol}
\begin{document}
$a \nperp b$, $c \not\perp d$
\end{document}


Finally, with the use of the fdsymbol package and its \nperp macro:

\documentclass{article}
\usepackage{fdsymbol}
\begin{document}
$a \nperp b$, $c \not\perp d$
\end{document}


Happy TeXing!

• Cannot load mathabx; LaTeX Error: Command \corresponds' already defined. Show a simple example how you do it! Commented Sep 9, 2011 at 5:24
• @user44967: The style used in your comment could easily be misunderstood to be a little harsh and demanding. You probably didn't mean it as such, but the imperative paired with the exclamation mark are a bit off-putting. Maybe a better way to phrase a request for clarification would be "Could you show a simple example of how to use your solution?".
– Jake
Commented Sep 9, 2011 at 11:30
• SORRY! Could you show a simple example of how to use your solution? and ... THANKS for your help Commented Sep 9, 2011 at 12:09
• @user44967: I trust that the two MWEs I've provided in the meantime meet your needs.
– Mico
Commented Sep 9, 2011 at 13:14

You can add a \not in front of it:

a \not\perp b
`

This gives you a struck through orthogonal symbol.