How different are the various varieties of Arabic?

Factual Questions
1

I understand that Modern Standard Arabic is nobody’s mother tongue, and that everyone who grows up with Arabic as a first language learns one of the many regional variants. What I don’t know, and would like to find out, is how much those variants differ from each other and from MSA, whether they’re all mutually intelligible (I suspect they are; I’ve never heard otherwise.), and how much those differences come through in written Arabic.

Also, how archaic is the Arabic of the Koran these days?

2

Arabic dialects can be very different. The Moroccan dialect especially, is very different from MSA, to the point of being unintelligable to other Arabic speakers. Though, for the most part, speakers can understand each other with a bit of effort. It’s not too much different than a Spanish and an Italian trying to communicate.

Classical Arabic (the language of the Qur’an) is archaic and overly formalized. For example, in written MSA vowels (the diacritics–which look like various types of apostrophes to English speakers) are not normally written because they are most often implied in context. However, in the Qur’an, things are much more structured and explicit.

3

Forgot to point out that dialects are spoken, not written. All newspapers and business/government documets are printed in MSA. Broadcast media is also normally in Modern Standard (or less frequently, Egyptian Arabic, which is the most wildly understood Arabic dialect through the Mideast/Northern Africa). So it’s pretty unlikely that an Arabic speaker couldn’t communicate with another speaker, despite their dialects.

4

ShortBus: A lot of interesting information. Thanks.

5

That’s not really a language thing so much as a religious thing, though. Vowels are written in the Qur’an in order to take no risk whatsoever with God’s word being distorted. It’s not the case that it was the norm to write down vowels during the period when the Qur’an was written. Interestingly, a system of diacritics to mark vowels was invented for Hebrew for precisely the same reason - in order to preserve a holy text (in this case, the Torah) without risking alterations.