What is the characteristic of hair that reflects light called?

The characteristic of hair that reflects light is called sheen. Sheen refers to the luster or shine that appears on the hair's surface, resulting from how light interacts with the hair's outer cuticle layer. Healthy hair typically has a natural sheen, which indicates that it is well-moisturized and free from damage. This reflectivity can be influenced by different factors, including the hair's texture, condition, and the products used on it.

Texture refers to the physical structure of the hair, such as whether it is straight, wavy, or curly, rather than its light-reflecting properties. Brightness is a term that may describe how light or dark a color appears, but it does not specifically describe the reflective quality. Color pertains to the hue of the hair rather than its ability to reflect light. Therefore, sheen stands out as the most accurate term for the light-reflective characteristic of hair.