What type of hair structure determines the hair's texture?

The shape of the hair follicle is indeed a crucial factor that determines hair texture. Hair texture can vary significantly due to the shape of the hair shaft as it emerges from the follicle. For instance, straight hair typically grows from round follicles, wavy hair emerges from oval-shaped follicles, and curly hair originates from more flattened or elliptical follicles. This relationship means that the inherent structure and formation of the follicle directly influence the way hair appears in terms of smoothness, curliness, or waviness.

Other aspects such as the diameter of the hair strand, hair color, and hair length do play roles in the overall characteristics of hair, but they do not fundamentally define its texture. Hair diameter might influence the perception of thickness or fullness, hair color does not affect texture, and hair length can alter the styling options but does not change the texture itself. Therefore, focusing on the follicle's shape offers the most relevant insight into understanding hair texture.