Which of the following is NOT a classification of hair types?

The classification of hair types typically includes categories that describe the natural texture and shape of hair strands. Common classifications are straight, wavy, and curly, which define the patterns of the hair. Each of these types has distinct characteristics that affect how hair behaves and what products or techniques are best suited for styling and maintenance.

Knotted does not represent a hair type but rather a condition or state of the hair, typically referring to tangles or matting that can occur regardless of the hair's natural type. While knotted hair can affect the styling process or maintenance, it doesn’t classify the structural attributes of the hair itself, which is why it's not considered a valid classification among hair types. Understanding the proper classifications helps stylists choose appropriate cutting and styling techniques tailored to each client's hair type.