Damit würde ich beispielsweise folgende Lösung vorschlagen:
% arara: pdflatex
% arara: makeglossaries
% arara: pdflatex
\documentclass{scrartcl}
\usepackage{siunitx}
\usepackage{glossaries,longtable}
% für die Bequemlichkeit einen \nomenclature Befehl:
\newcommand*\nomenclature[5][A]{%
\ifx#1A\relax
\newglossaryentry{#2}{
name={#3} ,
description={#4} ,
sort={#2} ,
user1 = {#5} ,
parent={abbreviation}
}
\fi
\ifx#1L\relax
\newglossaryentry{#2}{
name={#3} ,
description={#4} ,
sort={#2} ,
user1 = {\unexpanded{#5}} ,
parent={latin}
}
\fi
\ifx#1G\relax
\newglossaryentry{#2}{
name={#3} ,
description={#4} ,
sort={#2} ,
user1 = {\unexpanded{#5}} ,
parent={greek}
}
\fi
}
% einen neuen glossary-Style zur persönlichen Anpassung
\newglossarystyle{nomenclature}{%
\renewenvironment{theglossary}%
{\begin{longtable}{llp{\glsdescwidth}}}%
{\end{longtable}}%
\renewcommand*{\glossaryheader}{}%
\renewcommand*{\glsgroupheading}[1]{}%
\renewcommand*{\glossaryentryfield}[5]{%
\glsentryitem{##1}% Entry number if required
\bfseries\glstarget{##1}{##2}% Name
\\% end of row
}%
\renewcommand*{\glossarysubentryfield}[6]{%
\glstarget{##2}{##3}% Name
& \glsentryuseri{##2}% Units
& ##4% Description
\\% end of row
}%
\renewcommand*{\glsgroupskip}{\\}%
}
% Gruppen:
\newglossaryentry{abbreviation}{name={Abbreviations},description={dummy}}
\newglossaryentry{latin}{name={Latin Symbols},description={dummy}}
\newglossaryentry{greek}{name={Greek Symbols},description={dummy}}
% \nomenclature[Gruppe]{ID}{Symbol}{Beschreibung}{Einheit}
\nomenclature[G]{alpha}{$\alpha$}{Angle}{\si\degree}
\nomenclature[L]{V}{$V$}{Volume}{\si{\cubic\metre}}
\nomenclature[A]{UN}{UN}{
The United Nations (abbreviated UN in English, and ONU in French and Spanish),
is an international organization whose stated aims are facilitating cooperation
in international law, international security, economic development, social progress,
human rights, and achievement of world peace.
}{}
\nomenclature[L]{U}{$U$}{Voltage}{\si{\volt}}
\makeglossaries
\glossarystyle{nomenclature}
\begin{document}
\glsaddall
\printglossaries
\end{document}
