Ich öffne die Tür, wenn ich nach Hause komme.

to come

Breakdown of Ich öffne die Tür, wenn ich nach Hause komme.

• ich: I
• nach: to
• die Tür: the door
• öffnen: to open

Questions & Answers about Ich öffne die Tür, wenn ich nach Hause komme.

Why does the sentence use die Tür in the accusative case, and not a different article?

In German, die Tür (the door) is the direct object of the verb öffnen (to open). Direct objects in German normally take the accusative case, which is why you see die Tür instead of, for example, der Tür or dem Tür.

Why is wenn used here, and not wann?

Wenn is used for conditional or temporal clauses where the event is certain or repeated—like if/when I come home. Wann is only used when asking a question about time, e.g., Wann kommst du nach Hause? (When are you coming home?).

Is there any special word order rule I need to remember because of the wenn clause?

Yes. In a wenn clause (subordinate clause), the conjugated verb—here komme—goes to the end of that clause. After this subordinate clause, you often come back to the main clause word order. So you get:
Main clause: Ich öffne die Tür
Subordinate clause: , wenn ich nach Hause komme (with the verb at the end).

Why do we say nach Hause instead of zu Hause?

Use nach Hause when you are moving to your home (motion towards home). Use zu Hause when you are already at home and referring to your location. In the sentence, you are describing going home, so nach Hause is correct.