how would i know if it is plural? "Your plates?"
You don't. This sentence could refer to any number of plates.
I’d like to know this too..
If the context says it’s plural then the above sentence can be plural?
"Your dish is on the table" should be accepted.
Dish also means a kind of meals to American.
A plate IS a dish.
You didn't make note of the use of 上 after 桌子, which altogether specifies the location of 盘子.
Your plate is on top of the table. - wrong?