Again, just because we can trace a word to its three letter root does not mean we have found the core of its meaning.
But the Quran does not exist in a vacuum. There are mountains of books written about this very thing, and they date back to very early times in Islamic history. These books of commentary on the Quran, known as Tafsir, are about exactly this issue. They are like dictionaries of the Quran, from the time of the Quran's revelation. There are Hadith too, sayings of prophet Muhammad, which have been collected, and which outline in terms of practice, exactly how the Quran is to be interpreted.
Now Hadith and tafsir are not free of errors and contradictions like the Quran is, but they are also a key part of understanding the language, which helps in interpreting the text. The point is that all of this surrounding material has really helped to preserve the Arabic language.
If you read about the development of modern Hebrew, you will see that it was almost completely broken off from it's ancient sources. It is a new language with some passing similarities to ancient Hebrew:
http://en.wikipedia.org/wiki/Revival_of_the_Hebrew_languageArabic never underwent such a change. It had never died as a language, so there is a continuous tradition of it's usage dating back to the prophet Muhammad, and even to times before Islam.
Furthermore, the differences of opinion which occur among Muslims ,are not over linguistic issues. They are over interpretation, priorities, and conditions, and are almost entirely rooted in squabbles over hadith literature. The Shi'ah (islam's oldest sect) have the exact same Quran as the Sunni. It is the interpretation of hadith which fuel the differences between the two sects, not linguistic issues with the Quran.
