This is the 2nd most frequent Urdu word.
کی
The Urdu word "کی" is a postposition that indicates possession or relation and is equivalent to "of" or "'s" in English.
In this sentence, 'کی' is used as a possessive marker indicating ownership or affiliation between 'کتاب' (book) and 'قیمت' (price).
یہ کتاب کی قیمت زیادہ ہے۔
The price of this book is high.
In this sentence, 'کی' is used twice: first to indicate possession (belonging) between 'دوست' (friend) and 'مدد' (help), and second as a verb ending form associated with the feminine gender and past tense for the verb 'کرنا' (to do).
میں نے دوست کی مدد کی۔
I helped a friend.
Here, 'کی' functions to describe the association between the noun 'کل' (yesterday) and 'بارش' (rain), indicating a temporal relationship.