Possessive Adjectives and Possessive Pronouns

• El mío, la mía, los míos, las mías (mine).
• El tuyo, la tuya, los tuyos, las tuyas (thine).
• El suyo, la suya, los suyos, las suyas (his, hers, theirs, yours,polite).
• El nuestro, la nuestra, los nuestros, las nuestras (ours).
• El vuestro, la vuestra, los vuestros, las vuestras (yours familiar).

The Possessive Pronoun must be preceded by the definite article except when it follows the verb "to be" ("Ser") and ownership is asserted.

Examples:

Su casa es más importante que la mía: His firm is more important than mine.

V. ha acabado su trabajo, pero yo no he principiado el mío: You have finished your work, but I have not started mine.

Estos títulos y acciones son míos: These bonds and shares are mine (viz., belong to me).[2]

Possessive Adjectives Emphatic. If any emphasis is placed on the possessive adjectives, the forms of the possessive pronouns are used, following the noun, as:
Quiero la maleta mía y no la de su amigo: I want my portmanteau, not your friend's.

"A friend of mine," "a customer of yours" will be translated "un amigo de los míos," "un cliente de los suyos," or also "un amigo mío," "un cliente suyo," without the preposition "de."

The Possessive Pronoun preceded by the neuter article lo denotes "property in general," as:
Lo mío (mine--that which is mine).
Lo nuestro (ours--that which belongs to us).
Lo suyo or lo propio (one's own property).
Lo ajeno (other people's property (that which belongs to others)).

In addressing a person translate "my," etc., by "mío," etc., as:
Amigo mío: My friend.
Muy Señor mío (usual introduction to a Spanish letter).

But if the noun is qualified by an adjective, both "mi" and "mío" are
used ("mi" is more general), as Mi querido amigo (my dear friend).