Nubians and Sudanese differed linguistically but Egyptians erased the difference.

Evidence

Many Nubians did not speak Arabic at home, and they picked up what vocabulary they could when working in the cities of Egypt. Many Sudanese from the North came to Cairo as native speakers of Arabic. It was rare indeed for such a distinction to be made, so that in the work of most Egyptian writers of the period it is hard to find a Sudanese eloquent in spoken classical Arabic. — Eve M. Troutt Powell, A Different Shade of Colonialism_…, 311

Categorization

• DEFINE: Clarifies the actual linguistic distinction between Nubian (non-Arabic speakers) and northern Sudanese (Arabic speakers) that Egyptian writers collapsed.