documentclass{book}
usepackage{siunitx}
usepackage[acronym,toc]{glossaries}              % use glossaries-package


setlength{glsdescwidth}{15cm}

newglossary[slg]{symbolslist}{syi}{syg}{Symbolslist} % create add. symbolslist


glsaddkey{unit}{glsentrytext{glslabel}}{glsentryunit}{GLsentryunit}{glsunit}{Glsunit}{GLSunit}

makeglossaries                                   % activate glossaries-    package


% ==== EXEMPLARY ENTRY FOR SYMBOLS LIST =========================================
newglossaryentry{sig}{name=ensuremath{sigma},
    description={This is a non-bold stress scalar},
    unit={si{megapascal}},
    type=symbolslist}

newglossaryentry{csig}{name=ensuremath{boldsymbol{sigma}},
    description={This is a bold Cauchy stress tensor},
    unit={si{megapascal}},
    type=symbolslist}


% ==== EXEMPLARY ENTRY FOR ACRONYMS LIST     ========================================
newacronym{frp}{FRP}{Fiber Reinforced Polymers}


newglossarystyle{symbunitlong}{%
setglossarystyle{long3col}% base this style on the list style
renewenvironment{theglossary}{% Change the table type --> 3 columns
  begin{longtable}{lp{0.6glsdescwidth}>{centeringarraybackslash}p{2cm}}}%
  {end{longtable}}%
%
renewcommand*{glossaryheader}{%  Change the table header
  bfseries Sign & bfseries Description & bfseries Unit \
  hline
  endhead}
renewcommand*{glossentry}[2]{%  Change the displayed items
glstarget{##1}{glossentryname{##1}} %
& glossentrydesc{##1}% Description
& glsunit{##1}  tabularnewline
}
}


begin{document}

    glsaddall

    printglossary[type=acronymtype,style=long]  % list of acronyms
    printglossary[type=symbolslist,style=symbunitlong]   % list of     symbols

end{document}