\documentclass[a4paper,8pt,twocolumn]{extbook}
\usepackage{amssymb, amsmath} % needed for math
\usepackage[utf8]{inputenc} % this is needed for umlauts
\usepackage[ngerman]{babel} % this is needed for umlauts
\usepackage[T1]{fontenc}    % this is needed for correct output of umlauts in pdf
\usepackage[margin=2.5cm]{geometry} %layout
\usepackage{hyperref}   % links im text
\usepackage{color}
\usepackage{framed}
\usepackage{enumerate}  % for advanced numbering of lists
\clubpenalty  = 10000   % Schusterjungen verhindern
\widowpenalty = 10000   % Hurenkinder verhindern

\hypersetup{ 
  pdfauthor   = {Martin Thoma}, 
  pdfkeywords = {German-English mathematics dictionary}, 
  pdftitle    = {German-English mathematics dictionary} 
} 

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\begin{document}
\section{A}
\underline{abgeschlossen} (adj.) closed
\section{P}
\underline{punktsymmetrisch} (adj.) centrally symmetric
\section{S}
\underline{streng monoton fallend} (adj.) strictly monotonically decreasing
\underline{streng monoton wachsend} strictly monotonically increasing
\end{document}
