Hello,
I used LaTeX for a long time before converting (with difficulty !) to ConteXt. For example, to define my new theorems, I used the amsthm package and I did this :

\newtheoremstyle{theoremdd}% name of the style to be used
  {\topsep}% measure of space to leave above the theorem. E.g.: 3pt
  {\topsep}% measure of space to leave below the theorem. E.g.: 3pt
  {\itshape}% name of font to use in the body of the theorem
  {0pt}% measure of space to indent
  {\bfseries}% name of head font
  {. ---}% punctuation between head and body
  { }% space after theorem head; " " = normal interword space
  {\thmname{#1}\thmnumber{ #2}\thmnote{ (#3)}}

\theoremstyle{theoremdd}
\newtheorem{thmd}{Theorem}[section]

I'm trying to do the same thing with ConTeXt but I can not do it completely :

\setupenumerations[
       before={\blank},
       after={\blank},
       text=Théorème,
       alternative=serried,
       title=no,
       prefix=yes,
       prefixsegments=chapter,
       way=bysection,
       right=.,
       titlestyle=bold,
       style=italic,
       width=broad,
       
]

\defineenumeration[theorem]


\starttext

\startchapter[title={First Chapter}]
\startsection[title={First Section}] 
  \dorecurse{2}{
    \starttheorem
      \input ward
    \stoptheorem}
\stopsection
\stopchapter

\startchapter[title={Second Chapter}]
\startsection[title={Second Section}] 
\dorecurse{2}{
    \starttheorem
      \input ward
    \stoptheorem}
\stopsection
\stopchapter  

\stoptext

Thanks

Fabrice