What determines the texture of hair?

The texture of hair is fundamentally determined by the shape of the keratin proteins that make up the hair strand. Keratin is a fibrous protein that occurs in various forms depending on its stability and the bonds formed within it. When the keratin structure is straight, the hair tends to be straight; when it is curved or wavy, the hair takes on a wavy or curly texture. This means that the physical structure of the hair at a molecular level significantly dictates how it behaves and appears, effectively determining whether it is silky, coarse, wavy, or straight.

Other factors may influence hair characteristics, such as humidity affecting frizz or density relating to how full the hair looks, but they do not define the fundamental texture of the hair itself. Color is purely cosmetic and does not affect the inherent properties of the hair's texture. Thus, the shape of the keratin is the central factor in determining hair texture.