What is the term used for the appearance of heaviness and density in hair concentration?

The correct term that refers to the appearance of heaviness and density in hair concentration is the weight line. When a haircut has a defined weight line, it is indicative of a clear demarcation where the hair thickness appears concentrated. This results in an overall look of fullness and body within the hairstyle.

Understanding this term is crucial for stylists as it plays a significant role in creating different shapes and silhouettes within a haircut. A weight line contributes to the structural integrity of the style, influencing how the hair falls and behaves. This contrasts with other terms such as volume, which typically refers to the amount of space the hair occupies or its lift from the scalp, and texture, which focuses on the surface feel and character of the hair strands. Bulking, on the other hand, relates more to the practice of removing weight from the hair to create movement and is not synonymous with density or heaviness.