In Arabic the possessive “my” is represented as a ي which acts as a مضاف إليه. This creates a rule known as مناسبة which simply states that the letter before the ي must take a kasra for pronunciation reasons. For example, if someone wanted to say “my book” and book was in the state of رفع it should be rendered as كتابُي. But as the rule of مناسبة kicks in, it will change the dhamma to a kasra resulting in كتابِي.
However, the “my” possessive pronoun, also known as ياء المتكلم also poses interesting and complicated scenarios.
To understand this, there is another important rule a student must be aware of that deals with dual (مُثَنَّى) and sound masculine plural (جمع المذكر السالم) words. When these two types of words are مضاف they drop their ن. For example, your teachers would be rendered as مُعَلِّمُوكَ where مُعَلِّمُونَ dropped its ن. The same goes for dual words.
The scenario gets interesting when one wants to combine these two rules, that is the “my” possessive pronoun alongside a sound masculine plural word. To analyze this let’s look at this example with all three possible states:
مَرَرتُ بِمُعَلِّمِيّIn this case the word مُعَلِّمِينَ is in the state of jarr because it follows a harf al-jarr. The ن will drop because it is مضاف to a ي.
The two ي will combine (إدغام) rendering مُعَلِّمِيّ
جاء مُعَلِّمِيّIn this case the word مُعَلِّمُونَ is in the state of raf’ because it is the doer (فاعل). The ن will drop because it is مضاف to a ي.
The و and ي will also combine (إدغام) rendering مُعَلِّمِيّ
رأيت مُعَلِّمِيّIn this case the word مُعَلِّمِينَ is in the state of nasab because it is the direct object (مفعول به). The ن will drop because it is مضاف to a ي.
The two ي will combine (إدغام) rendering مُعَلِّمِيّIn the next article I will explain what vowel should go on the ي and the rules surrounding it.