In this lesson on Arabic grammar, the focus is on the declension of nouns when they serve as the object in a sentence, known as “Al-Ism Al-Mansub.” When the noun is the object, it must end with a “fatha” if it is definite, and with a double “fatha” if it is indefinite. Examples are provided to illustrate how the object is marked according to these rules, demonstrating both definite and indefinite noun scenarios.