نحو: رجل عالم جاءني
For instance, ‘a learned man came to me’ initially presents a person under a description rather than by a unique name.
By contrast, «جَاءَنِي زَيْدٌ» directs attention to a particular person through a proper name. The adjective learned (عَالِم) qualifies the person, but multiple people may share that quality.
ExpressionIdentification
رَجُلٌ عَالِمٌA learned man; the individual may not yet be singled out.
زَيْدٌAn individual designated by a proper name.
جَاءَنِي زَيْدٌA report that this named individual came.
A class noun can be restricted by context, but contextual restriction is not identical to the word's being a proper name by designation.