Y'all is the contractive of 'you all'
It is plural, refering to two or more people. If you use it to refer to one person you
will sound ignorant and any nearby Southern
will know that you are not really from around those parts.
Very common in the South, it is rare to find someone (excluding
Florida, and that's only because of all the Yankees down there) that doesn't use y'all.
Saying y'all makes so much more sense than the ever-
popular you guys, you guyses, or even you all. It is much shorter and gets the point across much faster. And takes less breath.
It is never
ya'll. The 'a' is not a part of you, it's a part of all (you wouldn't spell it out as youa ll, would you?).
Phoebe: What're you doing tonight?
Greg: Chris and I are going to the movies. We're seeing *insert good movie here*
Phoebe: Y'all
suck! I've wanted to see that movie for forever!