Why isn’t the phrase “quid nomen tibi es” instead of “quid nomen tibi est”

Question

Same with “quid nomen mihi est.” why isn’t it “quid nomen mihi sum”? Does it have to do with mihi and tibi?

Answer 1

The subject of these sentences is nomen, so it takes est. It's like how we say "my name is" and "your name is", rather than *"my name am" and *"your name are".