Density
How many hairs grow on a given area of scalp, from thin to thick.
Also: hair density
Density is the number of hairs growing close together on the scalp. It is different from strand thickness: a person can have many fine hairs or fewer coarse ones. Stylists judge density by how much scalp shows when the hair is parted. Thick, dense hair often needs weight removed with layers or thinning; low-density hair may look fuller with blunt lines and fewer layers. Density can vary over the head, often lower at the temples.