Which hair type is identified as having the smallest diameter and being more fragile?

Fine hair texture is characterized by having the smallest diameter compared to other hair types. This finer structure makes it more susceptible to damage and breakage, rendering it more fragile. People with fine hair often need to use gentle hair care products and be cautious with heat styling tools, as the hair's delicate nature can lead to split ends and weakened strands.

In contrast, medium, coarse, and thick hair textures have a larger diameter and generally more strength due to the greater amount of keratin and other structural proteins. This enhanced robustness allows them to tolerate more aggressive styling and environmental factors without as much risk of damage, making fine hair distinct in its fragility.