عَمْرٌو فِي الدَّارِ
Translation: ʿAmr is in the house.
عَمْرٌو: nominative mubtadaʾ.
فِي: preposition.
الدَّارِ: noun made genitive by «فِي».
فِي الدَّارِ: prepositional phrase attached to an understood predicate-related element.
The preposition alone is not the predicate; analyse the phrase as a unit.