Megillah 17a
If the Megilah is Greek to you - that could be okay! The Mishna states that a Jew should hear the reading of the Megilah in Hebrew if he understands Hebrew. But for people who do not understand Hebrew they may hear the Megilah read in their own language. This means the Megilah should be written and read in their foreign language. This is because if it is in Hebrew and then directly translated into another language at the time of the reading this is considered like reading from memory and not from the scroll, which is not allowed.
The interesting thing is if a person does hear it read in Hebrew, even though he or she does not understand Hebrew, they have still fulfilled their obligation for the Mitzvah, since the directive is to hearthe text. Therefore the Talmud, on 18a, suggests that if the Megilah is written in Greek that could be just fine. The Talmud points out that this law is unlike the law concerning the reciting of the Shema prayer, where the directive is not only to hear but also to understand what has been said. Still, the Talmud wonders how this could even be called "hearing" the Megilah if the person doesn't understand a word of Hebrew.
