what are you
whatcha
/ˈwʌtʃə/AssimilationReduction
In real speech
What happens to the sounds
are almost disappears, and t + y blend into “ch”: what are you → “WHAT-cha”.
When to use it
Whatcha doing? Whatcha talking about? Casual, between friends. Can also mean what do you or what have you.
Casual → formal
Slang
whatcha
Neutral
what are you
Sound notes
Assimilation: neighbouring sounds change each other, e.g. t + y → “ch”, d + y → “j”.