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How can I achieve this style for definitions, theorems, ...? I only know the standard or "plain" style (bold for header, italics for body) for theorem-like environments.

  • Please tell us whether you employ the amsthm or the ntheorem package, or if you're open to using either one.
    – Mico
    Oct 30, 2021 at 11:03
  • 2
    I would prefer the amsthm theorem package.
    – Descrates
    Oct 30, 2021 at 11:58

1 Answer 1


Here's a solution that employs the machinery of the amsthm package to create a new theorem style called (why not?) descrates.

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\setlength\textwidth{11cm} % just for this example

%% See p. 9 of the user guide of the 'amsthm' package 
%% for the "\newtheoremstyle" macro:
   {3pt}% Space above
   {3pt}% Space below
   {}% Body font
   {}% Indent amount
   {\scshape}% Theorem head font % <-- small caps
   {.}% Punctuation after theorem head
   {.5em}% Space after theorem headi
   {}% Theorem head spec (can be left empty, meaning `normal' )

\theoremstyle{descrates} % switch to the newly create style

\setcounter{section}{1} % just for this example

A topological space is said to be \textbf{Lindelöf} if 
every open cover has a \textsl{countable} subcover.


Addendum: If one were to use the ntheorem package rather than the amsthm package, one would need to replace the \usepackage{amsthm} and \newtheoremstyle directives in the code above with the following code:

   {\item[\hskip\labelsep\scshape ##1\ ##2.]}%
   {\item[\hskip\labelsep\scshape ##1\ ##2\ (##3).]}
  • 1
    very elegant solution, thank you!
    – Descrates
    Oct 30, 2021 at 12:08

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