Interrogative Pronoun

Definition:

The Pronouns which are used for asking questions, are called Interrogative Pronouns; as,
i. Which is your pen?
ii. Who spoke to you?
iii. Whose is this book?
iv. Whom do you want to see?
v. What do you see here?

Difference between Interrogative Pronoun and Interrogative Adjective

Interrogative Pronoun	Interrogative Adjective
Which is your pen?	Which pen is your?
Whose is this book?	Whose book is this?