Ptolemy started a dynasty in Egypt—a royal family of several generations. So during this time Egypt’s royals were Greek/Macedonian.
The regular shmoes of Egypt spoke Egyptian and the ruling class spoke Greek. How did they communicate with each other? Well, often royal decrees were chiseled onto big stones which were set up in public places where they could be read. To make sure everybody got the message, a decree might be written in 3 writing systems: hieroglyphic, Demotic and Greek.
Back to the beginning of The Western Civ User’s Guide to Reading & Writing.