I'm trying to stylize my definitions/examples etc. a bit to have a more simple overview once finished. Im specifically trying to achieve this: Example But don't really know how to achieve it. I can only think of a thin vertically stretched box aligned to the left of the whole environment but failed at implementing it since I'm fairly new to tex.



\documentclass[a4paper, 12pt]{article}

\usepackage{amsmath, amsthm, amssymb, amsfonts}

% Theorem styles
    {}            % Space above, empty = `usual value'
    {}            % Space below
    {\itshape}    % Body font
    {}            % Indent amount (empty = no indent, \parindent = para indent)
    {\bfseries}   % Thm head font
    {}            % Punctuation after thm head
    {\newline}    % Space after thm head: \newline = linebreak
    {Definition \thmnumber{#2}\thmname{\hfill#1}}   % Thm head spec

  • amsmath has nothing to do with theorems; you mean amsthm. Please fix the title. Commented Apr 13, 2019 at 20:54

1 Answer 1


I propose this code entirely based on thmtools and the leftbar environment from the framed package:


\documentclass[a4paper, 12pt]{article}

\usepackage[showframe]{geometry} % showframe only for checking purpose. Remove for production.
\usepackage{amsmath, amsthm, amssymb}

  \def\FrameCommand{{\color{rulecolour}\vrule width 3pt} \hspace{10pt}}%
  \MakeFramed {\advance\hsize-\width \FrameRestore}}%

 \declaretheorem[style=customDefinition, numberwithin=section]{definition}




enter image description here

  • You're welcome. Note that it should break across pages if necessary, but I didn't test it
    – Bernard
    Commented Apr 13, 2019 at 19:37
  • Maybe remove the showfram so others dont get confused Commented Apr 13, 2019 at 20:20
  • It was there only to check every thing was placed as expected. I'll a word about it.
    – Bernard
    Commented Apr 13, 2019 at 20:25

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