Here's why:

* Component refers to a distinct and individual part that forms a larger whole. This can be applied to both physical and non-physical aspects of a system.

* Part is a more general term that can refer to any portion of a whole, including smaller, functional sub-units.

* Physical portion is a more specific term that emphasizes the tangible, material aspect of a part.

Therefore, "component" is the most fitting general term for the physical portion of a part, as it encompasses both the physical and functional aspects of the part.

For example, in a car, the engine is a component that is also a part of the car. The engine itself consists of many smaller parts, such as pistons, cylinders, and valves.