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the adjective which describes something is following the described word in defining or undefining , masculine or feminine , singular or plural
So, we put ال in front of the objective when the described noun is definite
eg: قابلت الرجل الكبير
قابلت رجلا كبيرا
قابلت رجالا كبارا
قابلت الرجال الكبار
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