Possessive adjectives are used to show ownership:
mi coche (my car), tu casa (your house)
You put the possessive adjectives before the noun.
There are six possessive adjectives:
mi(s) = my
mi ventana, mis ventanas
tu(s) = your (fam. sing.)
tu mano, mis manos
su(s) = his, her, your (formal)
su habitación, sus habitaciones
nuestro(-a, -os, -as) = our
nuestra clase, nuestras clases
vuestro(-a, -os, -as) = your (fam. pl.)
vuestro gato, vuestros gatos
su (s) = their , they (formal)
su foto, sus fotos
The first three persons singular have two forms: singular and plural. In these cases, don’t worry about the gender (masculine and feminine.)
mi bolígrafo – my pen
mi regla – my rule
tu cuaderno – your notebook
tu goma – your eraser
su profesor – his teacher
su profesora – her teacher
The possessive adjectives for the first and second person plural (nuestro and vuestro) have four forms: masculine and feminine. Each one has singular and plural.
nuestro diccionario (our dictionary)
vuestro perro (your dog)
nuestra mesa (our table)
vuestra escuela (your school)
nuestros diccionarios (our dictionaries)
vuestros perros (your dogs)
nuestras mesas (our tables)
vuestras escuelas (your schools)
The possessive adjective for the third person plural is the same that the possessive adjective for the third person singular. The context indicates which is meant.
Possessive adjectives agree with the nouns they modify. That is to say, they agree with the thing possessed, not the possessor.
tú (with the written accent) is the subject pronoun meaning “you” (informal).
tu (without the written accent) is the possessive adjective meaning “your” (informal).