The Personal a  
  The "personal a" is the name often given to the use in some cases of the particle a before direct object nouns. It is not to be confused with the preposition a, nor with the a used before prepositional pronouns in redundant constructions. It has no English equivalent.  
  • Its use is generally obligatory before direct object nouns referring to persons, and is repeated in cases of compound object phrases:
    • Veo a tus padres y a tu hermanan todos los días en el parque.
      • I see your parents and your sister every day in the park.
  • Voy a llamar a Juana.
    • I'm going to call Juana.
  • It is also often used optionally before objects referring to animals when these are pets, or other things that the speaker wishes to personalize or express acquaintance with:
    • Llevé a mi perro al veterinario.
      • I took my dog to the veterinarian.
    • Conozco muy bien a Nueva York.
      • I know New York very well.
  • It is generally omitted after tener:
    • Tengo dos hermanos y una hermana.
      • I have two brothers and one sister.