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}