No rule for this one
No ending or word group predicts the article of Tür. Learn it as a pair and say it out loud: die Tür.
die Tür
It's die Tür. Tür is feminine, plural die Türen.
Die Tür ist zu.
The door is closed.
No ending or word group predicts the article of Tür. Learn it as a pair and say it out loud: die Tür.