Possessive adjectives are used to express possession or ownership.
Possessive adjectives agree with the noun they qualify in gender and number, with the thing possessed, not with the person who owns or possesses the object.
Mi libro. My book.
Mis libros. My books.
Mi casa. My house.
Mis casas. My houses.
Tu libro. Your book.
Tus libros. Your books.
Tu casa. Your house.
Tus casas. Your houses.
Su libro. His book. Her book. Its book. Your (formal) book. Their book. Your (formal,plural) book.
Sus libros. His books. Her books. Its books. Your (formal) books. Their books. Your (formal, plural) books.
Su casa. His house. Her house. Its house. Your (formal) house. Their house. Your (formal, plural) house.
Sus casas. His houses. Her houses. Its houses. Your (formal) houses. Their houses. Your (formal, plural) houses.
Nuestro libro. Our book.
Nuestros libros. Our books.
Nuestra casa. Our house.
Nuestras casas. Our houses.
Vuestro libro. Your (informal) book.
Vuestros libros. Your books.
Vuestra casa. Your house.
Vuestras casas. Your houses.
1. “Mi, tu and su” have only two forms, singular and plural.
Mi libro. Mis libros.
Mi casa. Mis casas.
Tu libro. Tus libros.
Tu casa. Tus casas.
Su libro. Sus libros.
Su casa. Sus casas
2. “Nuestro” and “vuestro” has four forms, singular, plural, masculine and feminine.
Nuestro libro. Nuestros libros.
Nuestra casa. Nuestras casas.
Vuestro libro. Vuestros libros.
Vuestra casa. Vuestras casas.
3. We place the possessive adjectives before the nouns.
4. “Vuestro” is mainly used in Spain.
5. You need to distinguish “tu” (without the written accent) from “tú” (with the written accent).
“Tu” is a possessive adjective (your): Tu casa es grande. Your house is big.
“Tú” is a subject pronoun (you): Tú tienes una casa muy grande. You have a very big house.
6. As you can see “su” and “sus” have multiple meanings: his, her, its, your and their and it can be ambiguous.
Su casa: his house, her house, its house, your house (formal), their house.
To clarify the exactly meaning you can use the preposition “DE” followed by a prepositional pronoun.
His house. La casa de él.
Her house. La casa de ella.
Their house. La casa de ellos/ellas.
Your house. La casa de usted.
7. Finally, remember possessive adjectives are not used with clothes and body parts. A definite article is used instead.
I wash my hands. Me lavo las manos.
I put my shoes on and I left house. Me puse los zapatos y salí de casa.