Questions & Answers about رأينا الجبل من خلال النافذة.
Why does the weak verb "to see" look like رأينا instead of ending with an alif maqshura like in رأى (he saw)?
When a verb ends in a weak letter (like the alif maqshura in رأى), adding a subject suffix that starts with a consonant (like the نا for "we") forces the weak letter to revert to its original root letter. For this verb, the root is ر-أ-ي, so the weak letter becomes a regular ي.
Why use من خلال for "through"? Can I just say خلال النافذة?
In Modern Standard Arabic, من خلال is used for physical movement or looking "through" an object or space. If you use خلال on its own, it almost always means "during" a period of time.
Is النافذة in the genitive case here because of the preposition من?
It is in the genitive case (majrur), but technically it's because of خلال. The word خلال acts as the first part of an idaafa (possessive structure), forcing the noun that follows it into the genitive case, which means it takes a kasra.
What case ending belongs on الجبل (the mountain)?
It takes the accusative case (mansub) because it is the direct object—the thing that was seen. If you read the sentence with full vocalization, you would pronounce it with a fatha at the end: الجبلَ.