Use of Greek language without \textlatin{} \textgreek{} each word [duplicate]

Question

I am writing a thesis in Latex,using the babel library \usepackage[english,greek]{babel} But using \textlatin and \textgreek in every word is very frustrating. I tried using polyglosia library \usepackage{fontspec,xgreek,polyglossia} but i got errors in every compiler. Is there some way to use both texts without changing each word?

Code of main below:

\documentclass[a4paper,12pt]{report}
\usepackage[left=3cm,right=2.5cm,top=2.5cm,bottom=2.5cm]{geometry}
\usepackage[LGR]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english,greek]{babel}
\newcommand{\en}{\selectlanguage{english}}
\newcommand{\gr}{\selectlanguage{greek}}
\usepackage{amsmath,amsfonts,amssymb}
\usepackage[parfill]{parskip}
\usepackage[unicode]{hyperref}
\usepackage{bookmark}
\usepackage{cite}
\usepackage{graphicx}
\usepackage{subcaption}
\usepackage{float}
\usepackage{siunitx}
\usepackage{color}
\usepackage{kmath,kerkis}
\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhf{}
\fancyfoot[R]{\thepage}
% Redefine plain style, which is used for titlepage and chapter beginnings
% From https://tex.stackexchange.com/a/30230/828
\fancypagestyle{plain}{%
    \renewcommand{\headrulewidth}{0pt}%
    \fancyhf{}%
    \fancyfoot[R]{\thepage}%
}

\renewcommand{\headrulewidth}{0.4pt}
\setlength{\headheight}{15pt}
\rhead{ \chaptername }
\lhead{Έξυπνο Σπίτι}
\rfoot{\thepage}
\graphicspath{{../PICS/}}

\def\tl{\textlatin}
\def\tg{\textgreek}

\begin{document}
\include{cover}
\title{Υλοποίηση  ενός προσωπικού ψηφιακού βοηθού μέσω \textlatin{open-source} εφαρμογών}
\author{ΧΑΤΖΟΓΛΟΥ ΚΩΣΤΑΣ \\
\today
\href{mailto:[email protected]}{\tl{[email protected]}}}
\maketitle

\tableofcontents

\thispagestyle{empty}
\include{DOCUMENT/Εισαγωγή}
\include{chapter1}
\include{chapter2}
\include{chapter3}
\appendix
\include{acronyms}

\selectlanguage{english}

\bibliographystyle{IEEEtran}
\bibliography{IEEEabrv,references}

\end{document}

Answer 1

My preferred solution is to use babel in LuaLaTeX, which can automatically detect the script you’re using and change fonts.

\documentclass{article}
\usepackage[nil]{babel}
\usepackage{unicode-math}
\usepackage[svgnames]{xcolor}

\babelprovide[import=el, main, onchar=ids fonts]{greek} % can also do import=el-polyton
\babelprovide[import, onchar=ids fonts]{english}

\babelfont{rm}
          [Language=Default, Color=DarkGreen]{CMU Serif}
\babelfont[english]{rm}
          [Language=Default, Color=NavyBlue]{CMU Serif}
\babelfont{sf}
          [Language=Default]{CMU Sans Serif}
\babelfont{tt}
          [Language=Default]{CMU Typewriter Text}

\begin{document}
\title{Υλοποίηση ενός προσωπικού ψηφιακού βοηθού μέσω open-source εφαρμογών}
\author{ΧΑΤΖΟΓΛΟΥ ΚΩΣΤΑΣ}
\date{\today}
\maketitle

\section{Έξυπνο Σπίτι}

Some text in English and Ελληνικά.

\end{document}

I chose the CMU fonts as an example because they require the Script=Greek font feature to work properly, but I also, purely for testing, gave Greek and English different colors.

This is actually more complicated than necessary. In practice, the Latin and Greek scripts are similar enough that you could get away with using the same Unicode font for both. The downside is, you would not get proper hyphenation for the second language.

XeLaTeX does not support onchar=, but you can try to do this with the (unmaintained and buggy) package ucharclasses.

\documentclass[english, greek]{article}
\usepackage{babel}
\usepackage{unicode-math}
\usepackage[Latin, Greek]{ucharclasses}
\usepackage[svgnames]{xcolor}

\babelfont{rm}
          [Language=Default, Color=DarkGreen]{CMU Serif}
\babelfont[english]{rm}
          [Language=Default, Color=NavyBlue]{CMU Serif}
\babelfont{sf}
          [Language=Default]{CMU Sans Serif}
\babelfont{tt}
          [Language=Default]{CMU Typewriter Text}

\setTransitionTo{BasicLatin}{\begin{otherlanguage}{english}}
\setTransitionFrom{BasicLatin}{\end{otherlanguage}}

\begin{document}
\title{Υλοποίηση ενός προσωπικού ψηφιακού βοηθού μέσω open-source εφαρμογών}
\author{ΧΑΤΖΟΓΛΟΥ ΚΩΣΤΑΣ}
\date{\today}
\maketitle

\section{Έξυπνο Σπίτι}

Some text in English and Ελληνικά.

\end{document}

My recommendation is to use LuaLaTeX when you can and 8-bit font encodings from last century when you’re forced to, but if you’re forced to, here’s how.

\documentclass[english, greek]{article}
\usepackage[LGR,T1]{fontenc}
\usepackage[utf8]{inputenc} % The default since 2018.
\usepackage{babel}

\begin{document}
\title{Υλοποίηση ενός προσωπικού ψηφιακού βοηθού μέσω open-source εφαρμογών}
\author{ΧΑΤΖΟΓΛΟΥ ΚΩΣΤΑΣ}
\date{\today}
\maketitle

\section{Έξυπνο Σπίτι}

Some text in English and Ελληνικά.

\end{document}

Unlike the newer engines, this solution will only change the font, not load Greek or English hyphenation patterns. If you are sprinkling in only a few English words, this should not be too much of a problem. IF you do need to actually switch the babel language tag, for example because you need to write full sentences in English that hyphenate properly, you can use \foreignlanguage{english}{Some text} or \begin{otherlanguage}{english}.

If you do want to pair different font families for English and Greek in PDFTeX, you can do this with \substitutefont. This example uses TeX Gyre Termes for English and Tempora for Greek.

\documentclass[english, greek]{article}
\usepackage[LGR,T1]{fontenc}
\usepackage[utf8]{inputenc} % The default since 2018.
\usepackage{babel}
\usepackage{tgtermes}
\usepackage{substitutefont}

\substitutefont{LGR}{\rmdefault}{Tempora-TLF}

\begin{document}
\title{Υλοποίηση ενός προσωπικού ψηφιακού βοηθού μέσω open-source εφαρμογών}
\author{ΧΑΤΖΟΓΛΟΥ ΚΩΣΤΑΣ}
\date{\today}
\maketitle

\section{Έξυπνο Σπίτι}

Some text in English and Ελληνικά.

\end{document}

Also note that PDFTeX supports only precomposed characters, not combining accents.