# tcolorbox theorem numbering

\documentclass{article}
\usepackage{amsmath,amsthm,amssymb,parskip}
\usepackage{graphicx,float,hyperref}
\usepackage[margin=1in]{geometry}
\usepackage{titling,multicol}
\usepackage{tcolorbox}
\tcbuselibrary{theorems}
\newtcbtheorem{mytheo*}{}%
{colback=purple!5,colframe=blue!100!,fonttitle=\bfseries}{th}

\begin{document}

\begin{mytheo*}{title...}{}
text...
\end{mytheo*}

\end{document}


I am trying to make the theorem unnumbered, but I have not managed to figure out how to remove the number 1 and the colon that appear at the beginning of the theorem title. Does anyone know how to do this?

There is a misunderstanding by the OP what \newtcbtheorem does actually:

\newtcbtheorem{foo}{...}{...}{...} will actually define both the numbered theorem - like enviroment foo and foo*, so \newtcbtheorem{foo*} will actually define foo* and foo**, leaving foo* being numbered however and foo** is the unnumbered version.

See page 340 of current tcolorbox manual for a description of this.

In addition, hyperref should be loaded as last package as almost always in 98% of all cases.

As a reply to the comment below by Bryan-M-H:

The unstarred version of the theorem has an additional mandatory argument that is meant for the label, see the changed example where the label is given as {foo}, which is extended to th:foo since the definition of the theorem has th as label prefix.

Related (but not duplicate) Counter for tcolorbox

Also related (no duplicate too): Problem with tcolorbox package

\documentclass{article}
\usepackage{amsmath,amsthm,amssymb,parskip}
\usepackage[margin=1in]{geometry}
\usepackage{titling,multicol}
\usepackage[most]{tcolorbox}

\usepackage{graphicx,float}
\usepackage{hyperref}

\newtcbtheorem{mytheo}{My theorem}{colback=purple!5,colframe=blue!100!,fonttitle=\bfseries}{th}

\begin{document}

\begin{mytheo*}{}
text...
\end{mytheo*}

See \ref{th:foo}

\begin{mytheo}{Foo}{foo}
text...
\end{mytheo}

\end{document}


• I tried to use the unstarred version of this in the body of the document, but found that the first letter of my theorem text was eaten up. [The word "text" came out as "ext" in the pink box.] What do I need to change? \begin{mytheo}{Fowler's Folly} text... \end{mytheo} – Bryan M-H Feb 17 '18 at 14:25
• @BryanM-H: See my extended answer: You forgot the 2nd mandatory argument that is meant for the label of the unstarred environment. If you don't need a label, use {} – user31729 Feb 17 '18 at 15:17