I am trying to write an essay in Greek and I type Greek characters but it doesn't compile. I have downloaded both
greektex and program
Babylon but it seems that I can't make them work.
I likewise do not know exactly what you mean by "it doesn't compile".
Nevertheless, this is what I would do if I wanted to typeset Greek: I would use LuaLaTeX. With LuaLaTeX you could just type greek without any additional packages -- provided that you use a font that contains all the greek symbols (and accents) you are about to use.
If you decided that you also need other languages and scripts (English/Latin, Hebrew, Arabic) this all is no problem. Plus: you don't need to learn new syntax or commands if you switch from LaTeX2e to LuaLaTeX.
If you have only Greek text, then the following is a good setup for
In case you have a TeX distribution that hasn't
should work; but I recommend updating the TeX system. You realize that LGRx is not available when you get the following error message:
Of course, the