\documentclass{article}

\usepackage{glossaries}
\makeglossaries

\begin{document}

\newglossaryentry{foo}{name=Foo, description={always first}}
\newglossaryentry{bar}{name=Bar, description={may only succeed foo}}
\newglossaryentry{baz}{name=Baz, description={optional, after baz}, nonumberlist=true}

\gls{foo} is a variable. \gls{bar} is too. However, \gls{baz} is a functional.

% commented out the following line to simplify the MWE (uncomment if you like)...
% \printglossaries

\end{document} 