• With any definite person who is the direct object of a verb not using other prepositions:
No conozco al expresidente Clinton. El bombero busca a la niña perdida. |
I don't know former President Clinton. The fireman is looking for the lost child. |
But: Busco un secretario nuevo. (indefinite person)
Pienso en mi hermana con frecuencia. (Pensar already uses en) |
• Before any pronoun referring to people, such as alguien, alguno, nadie, ninguno, cualquiera:
No necesito a nadie. No veo a ninguno de ellos. ¿A quiénes invitas? No invito a cualquiera. |
I need no one. I don't see any of them. Who are you inviting? Not anyone. |
• When there might be ambiguity about which is subject and which is object:
La represión responde a la rebelión. | Repression is responding to rebellion. |
→ The personal a is normally not used after the verb tener, except for emphasis:
Tengo tres hermanos.Siempre tengo a mi madre.