Spanish Grammar/Personal "a"
The direct object of a sentence is the noun or noun phrase that is the recipient of the action of a transitive verb.
In Spanish, when the direct object is a person it is preceded by the preposition "a". This is called the "personal a". When the direct object is not a person, there is no personal a:
1. María esta esperando el autobus. – María is waiting for the bus.
2. María esta esperando a John. – María is waiting for John.
The personal a is not used for animals:
3. Jorge mira la vaca.
The personal “a” is not used after tener, or the verb haber (even if the direct object is a person).
4. Tengo una esposa hermosa. – I have a beautiful wife.
5. Hay una mujer en la puerta. – There's a woman at the door.
If the direct object is an indefinite person, the personal “a” is not used. The person is considered grammatically “depersonalized.”
6. Busco novia. – I'm looking for a girlfriend (any girl).
7. Necesito médico. – I need a doctor (any doctor).