Why always followed by an a?

Question

Hola,I've seen this pattern and just learned it by rote, but I'm wondering why when I see venir and salir, and probably others I can't recall right now, the preposition follows the verb?Usted normalmente sale a comer a las dos. (You usually go out to eat at two o'clock.)Why isn't it sale comer a las dos, or Vienen nadar todos los domingos? I guess some rule has bypassed me at some point? What I'm most concerned is that past venir and salir, I'm going to get it wrong with other verbs.Muchas gracias,

Accepted Answer

Hola Stuart,
It is to do with "purpose" and "movement verbs". It happens generally with "ir", "salir" and "venir". You could also use "para" with the same meaning but these verbs tend to take the "a" more naturally:

"Fui al taller a recoger mi coche." (I went to the garage to pick up my car.)
"He venido a recoger mi coche." (I came to collect my car.)
"Hemos salido a comprar el pan." (We went out to buy some bread.)

All these imply movement and purpose. 
If you use a static verb, the "a" wouldn't be very welcome. For example:

"Estoy en el taller a recoger mi coche."  (incorrect)
"Estoy en el taller para recoger mi coche."  (correct)

I hope this helped.
Inma