a- can be interpreted her as a prefix. This prefix was productive during Old English. Today, await is considered as a full (lexic) word/verb, not being a prefix and a verb (a + wait). You will find await in the dictionary, as well as wait. The meanings of those words are slightly different.

This website shall be your new best friend: http://www.etymonline.com/index.php?term=a- You'll see that the a- prefix can have several meanings, depending on the origin of the word. Even then, that guideline isn't followed (eg. await)

Sorry XRIZz, I don't know either. Conjunction maybe...