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#  Introduction

Greek language is written with a special alphabet, for this reason some packages have to be included in the preamble to support it.

documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[greek]{babel}
\usepackage[LGR]{fontenc}

\begin{document}

\tableofcontents

\begin{abstract}
Αυτή είναι μια σύντομη περιγραφή του θέματος
σαφέστερα εξηγείται στο παρόν έγγραφο
\end{abstract}

\section{εισαγωγή}
Αυτό είναι το πρώτο τμήμα του εγγράφου.
Είναι μια εισαγωγική παράγραφο.

\section{δεύτερο τμήμα}
Το δεύτερο τμήμα του εγγράφου. Αυτή η ενότητα
μπορεί να περιέχει μαθηματική σημειογραφία.

There are some packages in this document related to the encoding and special characters. These packages will be explained in the next sections.

#  Input encoding

Modern computer systems allow you to input letters of national alphabets directly from the keyboard. In order to handle a variety of input encodings used for different groups of languages and/or on different computer platforms LaTeX employs the inputenc package to set up input encoding. This package properly display characters in the Greek alphabet, to use this package add the next line to the preamble of your document:

\usepackage[utf8]{inputenc}

The recommended input encoding is utf-8. You can also use other encodings depending on your operating system, for instance, iso-8859-7 will also support Greek characters.

#  Font encoding

To proper LaTeX document generation you must also choose a font encoding which supports specific characters from Greek language, this is accomplished by the fontenc package:

\usepackage[LGR]{fontenc}

The default LaTeX encoding is T1.

#  Language-specific packages and commands

Basic language functionalities are achived by importing the babel package for the Greek language in the preamble.

\usepackage[greek]{babel}

Default LaTeX capabilities can be extended. Let's see a complete example with Latin and Greek characters.

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[greek]{babel}
\usepackage{alphabeta}

\usepackage[LGR, T1]{fontenc}

\begin{document}

\tableofcontents

\begin{abstract}
Αυτή είναι μια σύντομη περιγραφή του θέματος
σαφέστερα εξηγείται στο παρόν έγγραφο
\end{abstract}

\section{εισαγωγή}
Αυτό είναι το πρώτο τμήμα του εγγράφου. Είναι
μια εισαγωγική παράγραφο.

\section{δεύτερο τμήμα}
Το δεύτερο τμήμα του εγγράφου. Αυτή η ενότητα
μπορεί να περιέχει μαθηματική σημειογραφία.

$x^2 + y^2 - \alpha = 4τ + 5α$

\textlatin{Latin text can also be added to
the document.}

\end{document}

The babel package will take care of the hyphenation and will automatically tanslate some elements in the document, such as the table of contents and the abstract. Below is a description of the rest of the commands.

\usepackage{alphabeta}
This package allows to put greek characters in mathematical mode. Instead of usign the comands \alpha, \beta, \gamma and so on you can use directly the keyboard input, as shown in the equation of the example.
\usepackage[LGR, T1]{fontenc}
This command will set two encodings for the fonts in this document. LGR for Greek text and T1 for Latin text.
\textlatin{}
Inside the braces of this command you can put text in Latin characters. Useful for brief anotations.

Notice also that in mathematical mode the Latin characters work properly, even if the T1 encoding is not set.