Some interesting Egyptian verbal forms

The form فـِــعـِــلْ is an Egyptian form that denotes a subject who is an expert at doing the action.

For example, حـِــرِ كْ and رِ وِ شْ are purely Egyptian words that indicate expertise at their respective actions, namely maneuvering and dazzling.

The Egyptian dialect also changes existing forms. For example, the classical imperative form إ فْـــتـَــعِـــل is transformed to the Egyptian إفـْــتـِــعـِـــل and the reflexive imperative إنـْــفـَـــعـِـــل is transformed to إتـْــفـِـــعـِـــل - note the change of reflexive ن to ت .

Which confirms that the Arabic verbal form mechanism is a powerful and flexible syntactic tool to create new or derived meanings that can be used to fill voids in the language when faced with cultural changes or new situations. Those new syntactic forms describe new combinations of meaning, and the remarkable feature is that when a word in that new form becomes widely used and understood, other Arabic roots (and indeed, Arabized foreign roots as well) can undergo the same syntactic transformation and automatically be (semantically) understood, without prior convention.

This also points to the fact that language is a continuously changing body of conventions, subject to historical / cultural / social / environmental forces. In other words, language evolves.

Not entirely new

But there's the similar classical form "fa3el" فَعِل. Add to it the tendency to "kasr" كسر the beginings of words in Egyptian accent (Cairere mainly vs. Alexandrian for exaple) and you reach the same form. So it could be a phonetic change rather than a morphological one.

Likewise the change from noon ن to taa ت in the form you describe is attested in other semetic languages, specifically Aramaic, and may have existed in ancient North Arabian languages (now extinct) like Safaitic الصفائية, Thamudic الثمودية and Lihyan اللحيانية; from whence they entered the Egyptian, probably through later bedioun dialects affected by them or by Aramiac/Nabatian in Sinai and Badiat AlSham بادية الشام.

Remember the Passion of Christ, the movie? In the scene where the hasidic rabbis are playing the demagogy on the Jerusalimites, herding them towards calling for the execution of Yahshua, when the rabbis ask what should be done to someone who has plasphemed as such and such, the crowds shout يتصلب. Exactly the reflexive form you're describing.

Thanks for adding substance

Thanks for adding substance to this post. I'd be grateful if you could check my post Arabic verbal forms where I attempt, feebly so far, to find generic semantic transformations to the various forms.

Your observation of morphological vs phonetic is valid, insofar as one would want to distinguish between them. Are you aware of any work done to ascribe semantic value to single letters and diacritics, thereby unifying morphology and phonetics?

Great reference from the Passion of Christ. Concerning our topic, it is clear that today's Egyptian dialect has formed as a result of constant interaction with neighbouring ones.