# How can I combine superscript, math symbols together? For instance, Trex1−/−

I was using this command to have my output "Trex1−/−", where -/- will be in a superscript and TREX emphasized/italic. My command is \emph{Trex1} $^${\num{-}}$/$ $^${\num{-}} I get error message saying," undefined control sequence" and "missing { inserted"-what does this mean and how can I solve this? I noticed, even though overleaf makes the output fine, but any text following this symbol becomes italic and skips the margin and alignment.

• Not sure I understand what you desire, but to get "-/-" as a subsript you can use \emph{Trex1}${}^{-/-}$. What is \num{-} supposed to be? Dec 3, 2021 at 7:37
• I used \num{-} to add the minus sign, isn't it how we add mathematical symbols like plus or minus? Dec 3, 2021 at 7:39
• For a minus sign, just use - in math mode. That will have the proper spacing based on if it is a unary negtive $-5$ or a binary operator $7-5$. Dec 3, 2021 at 7:39
• This makes sense, many thanks! but what about these symbols without a number before or after these (+,-. ~)? Dec 3, 2021 at 7:44
• For the tilde see Correctly typesetting a tilde. The + and - can just be used directly in math mode. If you want to enforce unary spacing on those you can use {-} and {+}. Dec 3, 2021 at 7:52

It should be $^{-/-}$, because you want a single superscript, albeit composed of multiple characters.

But you possibly don't want math mode at all: \textsuperscript is your friend. Anyway, here are four proposals, take your pick.

\documentclass{article}

\newcommand{\trex}{\textit{Trex1}\textsuperscript{--/--}}

\newcommand{\trexA}{%
\textit{Trex1}%
\textsuperscript{--\negthinspace/\negthinspace--}%
}

\newcommand{\trexM}{\textit{Trex1}$^{-/-}$}

\newcommand{\trexMM}{\textit{Trex1}$^{-\!/\!-}$}

\begin{document}

\trex\ good?

\trexA\ better?

\trexM\ good?

\trexMM\ better?

\end{document}


You should not surround each symbol with $ . Use $ to enter or leave inline math, so surround the entire expression. \num isn't a standard command it isn't clear what you intend it to do. (The siunitix package has a command of that name but unrelated to this I think) so I think you want

some text  $\mathit{Trex1}^{-/-}$ some more text


but it is hard to be sure as you provided little context about the intended use here.