Whose pen is this?

whose Pronoun

— Whose is used to ask what person something belongs to. Whose is this? There's no name on it. Whose coat did you take? — Whose is used to join a relative clause about a person or thing. Children whose parents smoke are more likely to smoke themselves. This is a country whose language is dying. The girl in the picture, whose name is Marion Russell, was from my home town.

pen Noun

— A pen is a writing tool that uses ink. She sat down with pen and paper and started a letter to her aunt. He picked up his ballpoint pen, crossed out some words. — A pen is a small area with a fence around it, usually for animals. The pigs walked slowly around their pen.

pen Verb

— If you pen something, you compose it and write it down. The letter was penned by Shakespeare just before he died. I penned my first song when I was in college. — If you pen an animal, you put it in a pen. — If someone is penned in, they are in a place and cannot get out easily. Most of them were penned in watching the TV with their parents.

is Verb

— A form of the verb be when talking about someone or something else. He is late for class. Is it hot in here?

this Determiner

— You use this to show which thing or idea you are talking about. You use it when the thing or idea is close to you. This trip was a great idea. Which book is yours, this one or that one? — The known thing. This man went to the door.

this Demonstrative Determiner

— The thing indicated. This is my hand.