Yay and Yeah

I am constantly confused when I write and read yeah, yay, and yea. I copied the ideas from this site and thought I'd share with you:

• Yeah - pronounced ye-uh as in yes
  "Hey Jen, are you going to with us to the mall."- girl a; "Yeah, I’ll go"- girl b
• Yay - rhymes with and is a synonym of hooray. It’s used in cases of excitement.
  "Did I tell you I won an ipod?" - girl a; "No! Oh that is exciting. Yay!" - girl b
• Yah - is also an expression of agreement but there is no excitement.
  "Hey are you ready to go" - girl a; "yah" - girl b
• Ya - means you
  "How are ya?"
• Yea - is a very old-fashioned formal way of saying “yes,” used mainly in voting. It’s the opposite of—and rhymes with—“nay.”
  "All in favor say yea, all opposed nay."
• and if that wasn’t confusing enough yay can also refer to height, as in "when I was yay big" [holding hand up]

I was mostly surprised with the the word yea, because I didn't know it was used in voting and measuring.

One thing I really need to work on is spelling their correctly. If I spell it correctly it's because of spell check. I automatically spell thier like that. The other day Michael wrote it correctly and didn't give it a second thought. their theri theri thier thier their . Now I'm really confused.