Have you had your dinner?

[Aleaf]

Have you had dinner?
Have you had dinner already/yet?

if already and yet here redundant?
_________________
Try to change youself before you try to change others.

[Jamie (K)]

"Have you had your dinner already?"
This is something we say when we know that someone has had his dinner and we are surprised by it.

"Have you had your dinner yet?"
We're not sure he has had dinner, but we assume he's going to eat it at some point.

"Have you had dinner?"
We're not sure he has had dinner, and we're not sure if he plans to eat it. This gives almost the same feeling as the one with "yet".