This is a question I've been wondering, how exactly did the process of Arabisation of places such as the Levant and Egypt occur, and how long did the process occur.
The Arabisation of the Maghreb, Al-Andalus and Persia (mostly the failure of it in this case) is relatively well documented, but what about the areas that already spoke Semitic languages?
Surely it did not just occur as segments of the population became Muslim, there must have been a period where there was a large amount of Muslims who spoke languages such as Coptic or perhaps Syria as primary languages. Also, how quickly did they adopt Arabic/Arabian culture such as dress, naming customs etc, and leave their own communities behind.
Also, at what point was this process complete? The Abbasid/Fatimid 10th century? The Crusades? The Mamluke era?
The details of this cultural transition would be fascinating to hear about.