Two endings deserve special attention.
What happensExample
masculine plural loses Noon-e-I'raabi; a silent spelling Alif remains after Waawلَا يَفْعِلُوْا
feminine plural keeps its final subject-pronoun Noonلَا يَفْعُلْنَ
Do not confuse the retained feminine-plural Noon with Noon-e-I'raabi.