Questions & Answers about Ianua villae aperta est, et nos intramus.
Because ianua is in the nominative singular and it agrees with the verb phrase aperta est (has been opened / is open). In Latin, the subject is typically shown by case (nominative), not by word order. So ianua = the door is the thing being described as aperta.
Here villae is genitive singular, meaning of the villa: ianua villae = the door of the villa. (The dative singular of villa is also villae, but the meaning “to/for the villa” wouldn’t fit well with door; genitive possession is the normal reading.)
Aperta est is the perfect passive of aperire (to open): literally has been opened, often best translated as is open (a resulting state).
- aperit would mean (someone) opens (active, present).
- aperitur would mean is being opened / gets opened (passive, present).
So focuses on the door being in the opened state.