The idafa (الإضافة) or “construct phrase” is a way to express possession in Arabic. For example, “the professor’s office”, “car key”, “University of Damascus”, etc. The idafa is the way to say “x of y”, and there is no alternative way of expressing possessive relation between nouns. In Arabic, “the professor’s office” is worded in such a way to say “office of the professor” (مكتبُ الإستاذةِ - “maktabu al-ustathi”). “Car key” is worded as “key of a car” (مفتاحُ سيارةِِ - “miftahu sayaratin”), and “University of Damascus” is جامعةُ دمشق (”jamia’tu dimashk”).
Idafa (genitive) is also used for partitives, such as “cup of coffee” (فنجانُ قهوةِِ - “finjanu qahawatin”). Idafa can also be used to describe material that something is made of (e.g. wooden chair) - كرسىُ خشبِِ (”kursiyu khashabin”).
Rules of Idafa
1. The first noun of the idafa can be in any grammatical case, however the second noun is always in the genitive case (with a kasra “i” or double kasra “in”) ending.
2. If the idafa phrase is definite (e.g. the student’s book), the ال prefix is added to the second noun. Exceptions include phrases like “my father’s house”, where the ي is attached to والد to make it والدي. The first noun of the idafa will never have the definite prefix, nor will it ever have a possessive suffix.
3. If the first noun of an idafa phrase ends in a ta marbuta (ة), it is pronounced as a ت (ta).
4. Any adjectives describing the noun must follow the idafa phrase. For example, “the professor’s large office” (مكتابُ الإستاذِ كبيرُ).