Orsdxy

The following MWE

documentclass{article}

usepackage[utf8]{inputenc}

usepackage[many]{tcolorbox}



newtcbtheorem{defbox}{Definition}%

{   enhanced,

    arc=0mm,

    interior style={white},

    attach boxed title to top center= {yshift=-tcboxedtitleheight/2},

    fonttitle=bfseries,

    fontupper=itshape,

    colbacktitle=white,coltitle=black,

    boxed title style={size=normal,colframe=white,boxrule=0pt}

}



begin{document}



begin{defbox}{Theorem Name}

Description

end{defbox}



end{document}

Produces the following (cropped) output

But my editor also says that there is a runaway argument. Likely for the same reason, there is an out of place D before the tcbtheorem.

My error log (I think?) says

 main.tex, line 19

Runaway argument?



{

! Paragraph ended before tcb@theo@label was complete.

<to be read again> 

                   par 

l.19 D

      escription

I suspect you've forgotten a `}', causing me to apply this

control sequence to too much text. How can we recover?

My plan is to forget the whole thing and hope for the best.



! Extra }, or forgotten endgroup.

<argument> tcb@theo@label {par }

                                  {D}

l.19 D

      escription

I've deleted a group-closing symbol because it seems to be

spurious, as in `$x}$'. But perhaps the } is legitimate and

you forgot something else, as in `hbox{$x}'. In such cases

the way to recover is to insert both the forgotten and the

deleted material, e.g., by typing `I$}'.

While I partially understand what a runaway argument is, I haven't found it here, and I don't know what to do next.

Any help would be appreciated.

You are missing the <prefix> argument of newtcbtheorem (see page 340 of the manual) and the <label> argument of begin{defbox}.

With the <prefix> and <label> you can reference your theorem with ref{<prefix>:<label>}:

documentclass{article}

usepackage[utf8]{inputenc}

usepackage[many]{tcolorbox}



newtcbtheorem{defbox}{Definition}%

{   enhanced,

    arc=0mm,

    interior style={white},

    attach boxed title to top center= {yshift=-tcboxedtitleheight/2},

    fonttitle=bfseries,

    fontupper=itshape,

    colbacktitle=white,coltitle=black,

    boxed title style={size=normal,colframe=white,boxrule=0pt}

}{th}



begin{document}



begin{defbox}{Theorem Name}{mytheorem}

Description of theorem~ref{th:mytheorem}.

end{defbox}



end{document}