You’re already familiar with possessive case in English–when we show ownership of something. For example, we might say, “this is Amer’s book” or “this is the book of Amer.”

The possessive case has two elements:

  1. The possessor, i.e. the one who owns the thing. In this case, Amer.
  2. The possessed, i.e. the thing being owned. In this example, the book.

The possessive case in Arabic is the same. The possessed is called the mudaf, the possessor the mudaf ilayh. It’s easiest to think of them as the form of “the x of y” rather then “y’s x”.

In English, you write an apostrophe-s after the possessor–so “Amer” becomes “Amer’s”.

In Arabic, there are two rules–one for the mudaf, and one for the mudaf ilayh.

  1. The possessor takes kasra (becomes majruw)
  2. The possessed becomes definite (by virture of being possessed).

As a first attempt before we knew these rules, we might write “the book of Amer” as “al-kitaabu Amerun”. Applying our rules:

  1. Amerun becomes Amerin
  2. Al-kitaabu becomes kitaabu

So the final sentence is “kitaabu Amerin”.

What about Ahmed’s chair? kursiyu Ahmedin. Heaven’s gate? Baabu jannatin!

If you feel you understand this bit of grammar, post an example (Arabic/transliteration and English translation) in the comments. If you have any questions, comments, clarifications, etc. post those in comments too inshallah!

External Links: lesson on Possessive Case