curliness

Curliness is the attribute of being curled, coiled, or highly curved. It is a qualitative descriptor used across disciplines to indicate the extent of deviation from a straight or simple form. Unlike formal metrics, curliness is often assessed by observation or simple indices rather than a universal scale, though several field-specific measures exist to quantify it.

In human hair, curliness arises from the shape of the hair follicle, the microstructure of the keratin fibers, and the pattern of disulfide bonds. Genetic factors largely determine curliness, with environmental factors such as humidity and chemical treatments affecting it. Hair curliness is commonly categorized on scales that include straight, wavy, curly, and coily. The degree of curliness relates to mechanical properties such as bending stiffness, friction along the surface, and moisture distribution, which in turn influence styling, texture, and appearance.

Curliness also appears in fibers, textiles, plant anatomy, and other materials. In textiles and fibers, curliness describes how fibers coil or twist, influencing fabric texture, drape, and elasticity. In plants, curling is a functional trait seen in tendrils and vines that aids support and attachment. In engineering contexts, natural curliness of wires or cables can affect packaging, fatigue life, and organization, while excessive curliness may be undesirable for certain applications.

In mathematics, curl is a specific operator in vector calculus that measures rotation of a field. The term curliness is not a standard technical term, and formal discussion of curves uses curvature and torsion rather than a general notion of curliness. See also curvature, torsion, and curl (vector calculus) for related concepts.