what is it?
Short-form possessive adjectives are unstressed words placed directly before a noun to indicate who something belongs to. Spanish has five base forms — mi, tu, su, nuestro, vuestro — each corresponding to a grammatical person. They replace the definite or indefinite article; you never use an article and a short-form possessive together. They agree with the noun they modify (the thing possessed), not with the owner.
when to use it
Identifying the owner of a thing or person. Use a short-form possessive whenever you want to say that something belongs to, or is associated with, a particular person: mi libro (my book), tu amigo (your friend).
Before the noun, with no article. The possessive always comes immediately before the noun. Do not add el, la, un, una in front of it.
With body parts, prefer the definite article. When the owner is already clear from context — especially with body parts and clothing — Spanish normally uses the definite article instead of a possessive: me duele la cabeza (my head hurts), not *me duele mi cabeza.
formation
Most short-form possessives have a single form for masculine and feminine nouns, changing only for number (singular/plural). Nuestro and vuestro are the exception: they also change for gender, like regular adjectives ending in -o.
| owner | singular (masc.) | singular (fem.) | plural (masc.) | plural (fem.) |
|---|---|---|---|---|
| yo (I) | mi | mi | mis | mis |
| tú (you, informal) | tu | tu | tus | tus |
| él/ella/usted (he/she/you formal) | su | su | sus | sus |
| nosotros (we) | nuestro | nuestra | nuestros | nuestras |
| vosotros (you all) | vuestro | vuestra | vuestros | vuestras |
| ellos/ellas/ustedes (they/you all) | su | su | sus | sus |
Note on su/sus. The form su/sus covers six different owners: his, her, your (usted), their (masculine), their (feminine), and your (ustedes). Context usually makes the meaning clear. When it does not, Spanish speakers rephrase with a prepositional phrase: el libro de él (his book), el libro de ella (her book).
examples in context
common pitfalls
Using a possessive with body parts. English says «my head hurts»; Spanish says me duele la cabeza, using the definite article. Writing *me duele mi cabeza is grammatically possible but unnatural and marked. When the owner is already identified by a reflexive or indirect-object pronoun, drop the possessive and use the article.
Adding gender endings to mi/tu/su. Only nuestro and vuestro change for gender. Mi, tu, su do not. The form *mia hermana does not exist in standard Spanish; the correct form is simply mi hermana.
Assuming su means only «his». The form su/sus covers his, her, your (usted), their (masculine or feminine), and your (ustedes). Translating it as «his» by default will lead to errors. When the meaning is ambiguous, clarify with de él / de ella / de usted / de ellos.