What is the difference between "Subhana Rabb al-Azim" and "Subhana Rabbi al-Azim"?

There is no difference between the phrases "My Lord, the Most Great" (ربيَ العظيم) and "Lord, the Most Great" (رب العظيم) from a linguistic perspective. In the first, the possessive ya (ياء الإضافة) is affirmed, while in the second, it is omitted for brevity. Both are permissible and found in the Arabic language and the Holy Quran.