# theorem word in italic not in bold

I want use theorem of LaTeX but I don't want the word "theorem" in bold. After I want like image in italic but not in bold. How set this? I only want change for observation and don't want change all "teorema" "lemma" etc,

Here make something similar:

Tweaking theorem style last parameter traps?

This is my preamble code:

\newtheorem{theorem}{Teorema}[section]
\newtheorem{cor}{Corolario}[theorem]
\newtheorem{lem}[theorem]{Lema}
\newtheorem{defin}[theorem]{Definición}
\newtheorem{ejem}[theorem]{Ejemplo}
\newtheorem{obsa}[theorem]{Observación}
\newtheorem{pro}[theorem]{Proposición}


The required theorem style is predefined:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[spanish]{babel}

\usepackage{amsthm}

\newtheorem{theorem}{Teorema}[section]
\newtheorem{pro}[theorem]{Proposición}
\newtheorem{cor}{Corolario}[theorem]
\newtheorem{lem}[theorem]{Lema}

\theoremstyle{definition}
\newtheorem{defin}[theorem]{Definición}
\newtheorem{ejem}[theorem]{Ejemplo}

\theoremstyle{remark}
\newtheorem{obsa}[theorem]{Observación}
\newtheorem*{nota}{Notación}

\begin{document}

\section{Prueba}

\begin{theorem}
\end{theorem}

\begin{pro}
\end{pro}

\begin{cor}
\end{cor}

\begin{defin}
\end{defin}

\begin{ejem}
\end{ejem}

\begin{obsa}
\end{obsa}

\begin{nota}
\end{nota}

\end{document}


• now work fine. thanks so much. i dont know about different style theorem and remark – user264522 May 9 at 16:04
\documentclass{article}

\usepackage{amsthm}
\usepackage{lipsum}

\newtheoremstyle{mythm}{3pt}{3pt}{}{}{\itshape}{:}{.5em}{}
\theoremstyle{mythm}
\newtheorem{mytheorem}{Theorem}

\begin{document}

\begin{mytheorem}
\lipsum[1]
\end{mytheorem}
\end{document}

• just what i need it. thanks so much – user264522 May 9 at 1:20
• i was looking, but it change all teorem style, only want observation – user264522 May 9 at 5:07