You use a noun phrase containing whose /huːz/ at the beginning of a relative clause to show who or what something belongs to or is connected with. Whose is used in both defining and non-defining clauses.
A noun phrase containing whose can be the subject or object of a verb, or the object of a preposition.
When whose is the object of a preposition, the preposition can come at the beginning or end of the clause.
You use whose in questions when you are asking who something belongs to or is connected with. Whose can be a determiner or a pronoun.
Whose is also used in reported clauses.
Don't confuse whose with who's, which is also pronounced /huːz/. When you write down what someone says, you can write 'who is' or 'who has' as who's. Don't write them as 'whose'.
whose is this? → ¿de quién es esto?
whose are these? (1 owner expected) → ¿de quién son éstos?; (2 or more owners expected) → ¿de quiénes son éstos?
I don't know whose it is → no sé de quién es
whose purse is this? → ¿de quién es este monedero?
whose cars are these? (1 owner expected) → ¿de quién son estos coches?; (2 or more owners expected) → ¿de quiénes son estos coches?
whose fault was it? → ¿quién tuvo la culpa?
whose car did you go in? → ¿en qué coche fuiste?
do you know whose hat this is? → ¿sabes de quién es este sombrero?
I don't know whose watch this is → no sé de quién es este reloj
those whose passports I have → aquellas personas cuyos pasaportes tengo, or de las que tengo pasaportes
the man whose hat I took → el hombre cuyo sombrero tomé
the man whose seat I sat in → el hombre en cuya silla me senté
the cup whose handle you broke → la taza a la que le rompiste el asa
In direct and indirect questions
As a relative
Whose book is this? → À qui est ce livre?
Whose pencil have you taken? → À qui est le crayon que vous avez pris?
Whose daughter are you?
BUT De qui êtes-vous la fille?.