"Hello and goodbye."
Translation:Γεια σας και αντίο.
It's just a shortening of the normal greeting as far as I can tell, I hear it a lot living in Greece at the moment. I hear it especially for goodbyes, αντιο I don't hear very often at all.
It's just like you can say both hello and hi in english or goodbye and bye.
I thought that γεια σας could mean either hello or goodbye. If that is correct could the answer to this question be Γεια σας και γεια σας?
Γεια σας και γεια σας would sound really odd in Greek though. It's almost like saying "Hello and hello" or "goodbye and goodbye" in English, since it's the same word, being repeated. The only case that someone could say γεια σας twice in the same sentence, is if there was someone kind of distinction between the two, or if the speaker greeted two different people or groups. ^.^