This is the 8th most frequent Urdu word.
ایک
"One"
Here, 'ایک' is used as a numerical adjective to signify the quantity of one.
مجھے ایک کتاب چاہیے۔
I need one book.
Here, 'ایک' functions as an adverbial phrase to indicate a nonspecific time, translating to 'one day' in English.
ایک دن میں نے عجیب چیز دیکھی۔
One day, I saw a strange thing.
In this sentence, 'ایک' is used as an article similar to 'an' or 'a' to specify 'an interesting story'.