Typesetting in Tamil For Multilingual Documents

 

When you are typesetting Multilingual document it doesn't make sense to load Polyglossia or Babel package just for a single line. All one has to load is the Fontspec package and the requisite font. Whenever Fontspec package is loaded it must be compiled in either XeLaTeX or LuaLaTex. Here is the minimal working example.

\RequirePackage[orthodox]{nag}
\documentclass[12pt,a4paper]{article}
\usepackage{fontspec}
\usepackage{ClearSans}
\usepackage{courier}
\newfontfamily{\TACtam}{Lohit Tamil}
\newfontfamily{\ctam}{Noto Sans Tamil Supplement}
\begin{document}
    normal  \emph{italic} \textbf{extra bold} \textit{italy} \texttt{help}
    {\TACtam அய்யா வணக்கம்.}{\ctam 𑿀}
\end{document}

You can name the Commands \TACtam and \ctam , wordings of your choice, this is saying to XeLaTeX to encode the fonts in Tamil.

 Reference: 

https://tex.stackexchange.com/a/241960/229186