Which term is used to describe the degree of fineness or coarseness in the texture of hair?

The term used to describe the degree of fineness or coarseness in the texture of hair is referred to as diameter. The diameter of hair relates directly to its width and can indicate how coarse or fine the individual strands are. Coarse hair typically has a larger diameter, while fine hair has a smaller diameter. Understanding the diameter is crucial for hair coloring and styling, as it influences the way products are absorbed, how the hair responds to treatments, and the final appearance after styling.

In contrast, density refers to the number of hair strands in a given area on the scalp, thickness refers to the width of an individual strand, and porosity describes the hair's ability to absorb and retain moisture. While these terms all relate to hair characteristics, diameter specifically addresses the size aspect which directly correlates with the texture of hair.