# Creating abbreviations list with manual entries

How do I create list of abbreviations if I want to add them manually and not tag each abbreaviation in the file first (the file is already written)?

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A simple tabular-like environment?

\documentclass{article}
\usepackage{longtable}

\newcommand\nomenclature[2]{#1 & #2 \\}

\begin{document}

\begin{longtable}{@{}p{1cm}@{}p{\dimexpr\textwidth-1cm\relax}@{}}
\nomenclature{$a$}{The number of angels per unit area}%
\nomenclature{$N$}{The number of angels per needle point}%
\nomenclature{$A$}{The area of the needle point}%
\nomenclature{$\sigma$}{The total mass of angels per unit area}%
\nomenclature{$m$}{The mass of one angel}
\end{longtable}

\end{document}

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