# How is this equality symbol different from a regular equality (=) symbol? [duplicate]

I encountered the following equality symbol in a paper (page 4, Eq 4). I am not sure how it is different from a regular equality (=) symbol.

What does this symbol mean? And how can I write it in latex?

• meaning of the mathematics is off topic here sorry, a tex question of how to typeset that would be on topic. (If I knew the meaning I'd have mentioned it here) – David Carlisle Oct 29 at 23:58
• Off topic: maybe it is only to explain from where that equality comes. Look for some equation named as (!). – Sigur Oct 29 at 23:59
• @DavidCarlisle Thanks for your input. Since you mentioned, I feel interested in how one would go about writing that symbol. – vvy Oct 30 at 0:00
• @Sigur I have flagged the post for migration. Thank you. – vvy Oct 30 at 0:03

OP comments: "I feel interested in how one would go about writing that symbol"

\documentclass{article}
\usepackage{stackengine}
\def\bangequal{\mathrel{\ensurestackMath{%
\stackengine{1pt}{=}{\scriptstyle!}{O}{c}{F}{F}{S}}}}
\begin{document}
$a \bangequal b$
\end{document}


To get the particularly ugly version where the ! is underlined...

\documentclass{article}
\usepackage{stackengine}
\def\bangequal{\mathrel{\ensurestackMath{%
\stackengine{0pt}{=}{\underline{\scriptstyle!}}{O}{c}{F}{F}{S}}}}
\begin{document}
$a \bangequal b$
\end{document}


• Nice. I don't know why but the image posted appears to have an underlined ! above =. Ugly. – Sigur Oct 30 at 0:15
• Oh nooo, please don't reproduce that... lol – Sigur Oct 30 at 0:17
• @Sigur My bad. It had underlined + highlighted in my draft, I removed the highlight but the underline remained. It's not there in the original paper. – vvy Oct 30 at 0:17
• @Sigur Too late..... – Steven B. Segletes Oct 30 at 0:18
• @Sigur Steven only needs to wrap \textcolor{white}{...} around it, then it is not too bad. ;-) – Schrödinger's cat Oct 30 at 0:54