After finishing the tree I discovered that the course does not introduce the cases used in Classical Arabic, though it uses them sometimes when pronouncing the sentences. So, I though to write a short explanation about them.
Classical Arabic has three cases (called الإعراب):
Nominative (مرفوع), used for the subject;
Accusative (منصوب), used for the direct object (and for some other verbal complements);
Genitive (مجرور), used for denoting possession and after prepositions.
Those cases sound differently according to the noun's state: for nouns that are either definite or are in the construct state, the endings are -
Nom: /-u/ ُ, Acc: /-a/ َ, Gen: /-i/ ِ .
Indefinite nouns have the same endings followed by /-n/ -
Nom: /-un/ ٌ , Acc: /-an/ ًا , Gen: /-in/ ٍ .
It must be stressed that these cases occur only with singular nouns and broken plurals. Sound plurals have a different way for displaying cases (the distinction between the suffixes /-uuna/ and /-iina/).
When added to a noun ending with ة, the taa2 marbuuTa will be pronounced as a ت: /-tu(n)/, /-ta(n)/, /-ti(n)/.
And here are some examples:
The pretty book: 2al-kitaabu 2al-jamiilu
A pretty book: kitaabun jamiilun
I read the book: qara2tu 2al-kitaaba
I read a book: qara2tu kitaaban
On the book: 3alaa 2al-kitaabi
On a book: 3alaa kitaabin
These are only the basics, there are more details regarding the cases’ uses and how they may manifest on nouns.
Hope it helped!