# Symbol for not an ideal

I'm trying to write the symbol for not an ideal. I've been using \lhd to represent an ideal so what I want is to put a line through this in the same way \neq or \nless do for \eq and \less.

Any suggestions?

• Is \not\lhd enough? – Sigur Feb 4 '15 at 9:39
• No, I tried that myself but unfortunately that produces the line before the \lhd symbol, so it's "misaligned". I want it to go through the symbol, just like I mentioned the \neq does. – An Aspiring Mathematician Feb 4 '15 at 9:44
• I'd simply say $I$ is not an ideal of $R$. Avoid symbol inflation. – egreg Feb 4 '15 at 9:47
• – karlkoeller Feb 4 '15 at 9:48
• Is \lhd a common symbol for ideals? I use it for normal subgroup. – Sigur Feb 4 '15 at 12:27

Use \centernot from the same package.

\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage{centernot}

\begin{document}

$\centernot{\lhd}$

\end{document}


• How did you generate that large image? The one I generated with standalone and saved as png with Acrobat looks like crap. – Juri Robl Feb 4 '15 at 9:51
• @JuriRobl Zooming-in in SumatraPDF and capturing the screenshot. – karlkoeller Feb 4 '15 at 9:52
• @stephenmg you're welcome. – karlkoeller Feb 4 '15 at 9:53

You can use either the generated symbol \not\lhd or the complete smybol \nlessclosed, both of which are from the MnSymbol package. Depending on the symbol packages you're already using, it may change some of the symbols to it's own.

\documentclass{article}
\usepackage{MnSymbol}
\newcommand{\notlhd}{\nlessclosed}
\begin{document}
$\nlessclosed$ $\notlhd$ $\not\lhd$
\end{document}


• You may want to add that MnSymbol changes most of the available symbols. – karlkoeller Feb 4 '15 at 10:00
• It depends what he is using at the moment, he may already be using it? But yes, I will add that. – Juri Robl Feb 4 '15 at 10:01