"It is a sandwich."
Translation:To jest kanapka.
Why is it "to jest kanapka (nominative case)" and not "to jest kanapką (instrumental case)"?
Does the verb "być" ("to be") not trigger the instrumental case when it is defining "To"?
Sentences starting from to jest (and it's equivalents in other tenses to był/to była/to było/to będzie) use nominative. In fact, you could argue that the noun on the right is the actual subject of the sentence in such cases, but I don't want to speculate too much.