This is the 12th most frequent Hindi word.
उन
"Them" (third person plural pronoun)
Here, 'उन' is used as a pronoun to refer to objects (books) that are previously mentioned or identified.
मैंने उन किताबों को पढ़ा है।
I have read those books.
In this sentence, 'उन' acts as a demonstrative pronoun referring to specific students.
उन छात्रों ने अपनी परियोजना पूरी की।
Those students have completed their project.
Here, 'उन' is a pronoun referring to particular questions being discussed.