In classical arabic "fusha" Different nouns can have different ways of getting in a certain case. It depends on the place of the word in the sentience. I can't explain them all at once..but if you learn it one by one you'll find it quite easy :) - how to say word "informal" in Arabic? You mean in "local dialects" → اللهجة العامية In local spoken dialect we don't use cases .. And mostly the words ends with sukun (ـْ) →" no vowel". Like the word: ْالإسم we pronounce it like : al-esm . Book:كتاب we pronounce it like : kitab I hope that this is the answer to your question.. Hope I helped :)

I really do not understand what are you asking about , but i think you mean الضمة والكسرة والفتحة The word in Arabic means الكَلِمَة not الإسم

Safy, thank you very much

The fourth case name is الجزم and one of its flags is السكون So السكون is just a result or a flag for the الجزم I hope I have answered your question, Reven. Safy Arabic teacher on italki.

Sana, thank you very much