The genitive case occurs in Arabic in two situations. Both of these situations occur very often in the language. First, a noun or adjective following a preposition will always be in the genitive. The only other time the genitive occurs is if a word is the second or later term of an idaafa. (The idaafa is discussed below.)
The genitive case marker is one kasra if a word is definite and two kasras if the word is indefinite. The second kasra is pronounced as a ن, just like the second dhamma in the nominative case.كتابٍ is an example of the indefinite genitive (pronounced “kitaabin”). الكتابِ is an example of the definite genitive (pronounced “alkitaabi”).