It has a Root-pattern morphology in which words optimally derive from a set of 3 or 4 consonants. To some extend those roots can even be grouped into meta roots.

Loan words do not easily slide into this. New words are less easily made up than e.g. in German, where you can just concatenate.

Lots of words have been around for a long time, since quranic Arabic influences the language still, and as a result have layers of meaning.