ألا ترى أن السواد جزء من مفهوم الأسود
Do you not see that blackness is a component of the concept “black”?
The adjective “black” involves more than the abstract word “blackness”: it relates a bearer to a quality. Blackness can form part of that composite meaning even when the degree of blackness differs among objects.
The point is methodological. Conceptual inclusion is not a promise that every instance realizes a property at the same intensity. Variation in degree does not eliminate the shared intelligible feature.