What is the Accusative case form of "der" in German?

For example, the sentence "Ich esse den Apfel."

In the given sentence, "Ich esse den Apfel," the word "Apfel" is a masculine noun. In German, "Apfel" is "der Apfel" in the nominative case. In the accusative case, for masculine nouns, the definite article changes from "der" to "den." Therefore, the correct sentence is "Ich esse den Apfel," which translates to "I eat the apple" in English. Remember that the nominative masculine definite article "der" changes to "den" in the accusative. This is crucial for constructing correct sentences in German. Keep practicing to familiarize yourself with these changes.