Is this sentence correct? An oven is a thing where you use to cook.
No. An oven is a thing that you use to cook.
I have the pencil. The pencil that you gave me yesterday.
I have the pencil that you gave me yesterday.
La Costa del Sol is a beach. You can swim and sunbathe.
La Costa del Sol is a beach where you can swim and sunbathe.
This is the city. I used to live.
This is the city where I used to live.
I dropped a glass. The glass was new.
I dropped a glass that was new.
The waiter was rude. The waiter was wearing a black suit.
The waiter who was wearing a black suit was rude.
The man is in the garden. The man is wearing a blue jumper.
The man who is wearing a blue jumper is in the garden.
She loves books. The books have happy endings.
She loves books that have happy endings.
A drugstore is a place. You buy medicine.
A drugstore is a place where you buy medicine.
My sister has three children. My sister lives in Australia.
My sister who lives in Australia has three children.