Este libro es mío.
English: This book is mine.
Possessive pronouns in Spanish are words that replace a noun and show ownership or possession, like 'mine', 'yours', 'ours' in English.
Use Spanish possessive pronouns when you want to say something belongs to someone, but you don't repeat the noun. They agree in gender and number with the thing owned, not with the owner.
Este libro es mío.
English: This book is mine.
¿Es este coche tuyo?
English: Is this car yours?
Las llaves son nuestras.
English: The keys are ours.
¿Dónde están los cuadernos suyos?
English: Where are their notebooks?
La casa grande es vuestra.
English: The big house is yours (plural).