جَاءَ رَجُلٌ عَالِمٌ: ʿĀlimun qualifies the one man; it is a naʿt, not another person who arrived.
جَاءَ رَجُلٌ وَامْرَأَةٌ: a man and a woman are both intended as arrivals; it is coordination.
Matching case endings alone do not establish coordination: the semantic relation and coordinating particle matter.
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Coordination (ʿAṭf bi-l-Ḥurūf): Rules and Parsing
جَاءَ رَجُلٌ عَالِمٌ: ʿĀlimun qualifies the one man; it is a naʿt, not another person who arrived.
جَاءَ رَجُلٌ وَامْرَأَةٌ: a man and a woman are both intended as arrivals; it is coordination.
Matching case endings alone do not establish coordination: the semantic relation and coordinating particle matter.