So here is our new sentence.

oJ PevtroV ejstin oJ didavskaloV.

You need to learn one more grammatical term this Section. oJ didavskaloV is called the predicate nominative. Why?

  • The "nominative" is easy. The word following eijmiv must be in the nominative.
  • The word "predicate" refers to the verb and what follows.

So the predicate nominative is the word following the verb eijmiv.

That's a lot of grammar, but I think you understand. If not, you need to ask your teacher for help.